JP2016018046A - Carrier for electrostatic charge image development, developer for electrostatic charge image development, developer cartridge, process cartridge, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carrier for electrostatic charge image development that can suppress a change in print density in the early stage of the start of use of a developer, and can suppress image defects while ensuring stable print density even after a long-term image formation under low temperature and low humidity.SOLUTION: There is provided a carrier for electrostatic charge image development that contains at least magnetic core material particles and a resin coating layer coating the surface of each of the magnetic core material particles, where the resin coating layer contains a resin including a monomer unit having a carboxyl group, and a surface layer of the resin coating layer has a crosslinked structure of the carboxyl group included in the resin and a di- or more valent metal.SELECTED DRAWING: None

Description

  The present invention relates to an electrostatic charge image developing carrier, an electrostatic charge image developing developer, a developer cartridge, a process cartridge, and an image forming apparatus.

  A method for visualizing image information through an electrostatic charge image such as electrophotography is currently used in various fields. In electrophotography, an electrostatic image (electrostatic latent image) is formed on an image carrier by an electrification process and an exposure process (electrostatic image formation process), and an electrostatic image developing toner (hereinafter simply referred to as “toner”). The electrostatic image is developed with a developer for developing an electrostatic charge image (hereinafter sometimes referred to simply as “developer”) (development process), followed by a transfer process and a fixing process. Visualized. The developer used here imparts an appropriate amount of positive or negative charge to the toner by triboelectrically charging both the carrier for developing an electrostatic image (hereinafter sometimes simply referred to as “carrier”) and the toner. The two-component developer and the one-component developer used alone, such as magnetic toner, are roughly classified. In particular, the two-component developer is widely used for reasons such as easy design because the carrier itself has functions such as agitation, conveyance, and charging, and the functions required for the developer can be separated. ing.

  Carriers are generally classified into a resin-coated carrier having a resin coating layer on the surface of magnetic core particles and an uncoated carrier having no resin coating layer on the surface. A developer using a resin-coated carrier has excellent charge controllability, and is relatively easy to improve environment dependency and stability over time. The resin-coated carrier is usually obtained by forming a resin coating layer on the surface of the magnetic core particles using a resin coating layer forming solution containing a resin and an organic solvent.

  In recent years, with the miniaturization of devices and the diversification of usage environments, the carrier has been studied to reduce the size and distribution of the particles, and various studies have been made such as the composition of the magnetic core particles and the composition of the coating resin layer. .

  In Patent Document 1, in a carrier for electrophotography having a resin coating layer on the surface of a core material, the resin forming the coating layer is an alicyclic methacrylate monomer and a chain methacrylate monomer. An electrophotographic carrier is described in which a specific amount of a surfactant and a monomer each remain in the resin coating layer.

  In Patent Document 2, in a carrier including a core material and a resin coating layer formed on the surface of the core material, the resin coating layer contains alumina particles, and the alumina of the resin coating layer measured by fluorescent X-ray analysis. A carrier is described in which the X-ray intensity of the particles is smaller than the X-ray intensity of the metal contained most in the core material of the core material measured by fluorescent X-ray analysis.

  In Patent Document 3, in a carrier for developing an electrostatic latent image having a resin coating layer in which the surface of magnetic particles is coated with a resin, the resin coating layer has a specific particle diameter in a resin layer mainly composed of an acrylic resin. There is described a carrier for developing an electrostatic latent image, characterized in that it contains silicone resin particles having a specific concentration.

Japanese Patent No. 3691085 JP 2007-78849 A JP 2010-145471 A

  The object of the present invention is to suppress changes in print density at the beginning of use of the developer, and to suppress image defects while ensuring stable print density even after long-term image formation under low temperature and low humidity. It is an object to provide an electrostatic charge image developing carrier, an electrostatic charge image developing developer, a developer cartridge, a process cartridge, and an image forming apparatus.

  The invention according to claim 1 includes at least a magnetic core particle and a resin coating layer covering a surface of the magnetic core particle, and the resin coating layer includes a resin including a monomer unit having a carboxy group. And an electrostatic charge image developing carrier having a crosslinked structure of a carboxy group contained in the resin and a metal having a valence of 2 or more in the surface layer of the resin coating layer.

  In the invention according to claim 2, the resin including the monomer unit having a carboxy group includes a copolymer resin of a (meth) acrylate monomer and a monomer containing a carboxy group and an ethylenically unsaturated group. Item 2. The electrostatic charge image developing carrier according to Item 1.

  The invention according to claim 3 is the electrostatic image developing carrier according to claim 2, wherein the (meth) acrylic acid ester monomer is an alicyclic methacrylic acid ester monomer.

  The invention according to claim 4 is an electrostatic charge image developing developer comprising the electrostatic charge image developing carrier according to any one of claims 1 to 3 and an electrostatic charge image developing toner.

  The invention according to claim 5 is for electrostatic charge image development comprising the electrostatic charge image developing carrier according to any one of claims 1 to 3 and external additive particles having a volume average particle diameter of 50 nm to 200 nm. And a developer for developing an electrostatic image containing toner.

  A sixth aspect of the present invention is a developer cartridge containing the developer for developing an electrostatic charge image according to the fourth or fifth aspect.

  The invention according to claim 7 contains the developer for developing an electrostatic image according to claim 4 or 5, and develops the electrostatic image formed on the surface of the image carrier with the developer for developing an electrostatic image. And a developing unit that forms a toner image, and is a process cartridge that can be attached to and detached from the image forming apparatus.

  According to an eighth aspect of the present invention, there is provided an image carrier, a charging unit that charges the surface of the image carrier, an electrostatic image forming unit that forms an electrostatic image on the surface of the image carrier, and the electrostatic image. An image forming apparatus comprising: a developing unit that forms a toner image by developing with the developer for developing an electrostatic image according to claim 4; and a transfer unit that transfers the toner image to a recording medium.

  According to the first aspect of the present invention, compared to the case where the surface layer does not have the cross-linked structure, the change in print density at the beginning of the use of the developer is suppressed, and long-term image formation under low temperature and low humidity. Later, there is provided a carrier for developing an electrostatic image in which image defects are suppressed while ensuring a stable print density.

  According to the invention of claim 2, the resin coating layer has a low temperature and low humidity as compared with the case where the resin coating layer does not contain a copolymer resin of a (meth) acrylic acid ester monomer and a monomer containing a carboxy group and an ethylenically unsaturated group. Provided is an electrostatic charge image developing carrier in which image defects are further suppressed after long-term image formation.

  According to the invention of claim 3, image defects are further suppressed after long-term image formation under low temperature and low humidity as compared with the case where the (meth) acrylic acid ester monomer is not an alicyclic methacrylic acid ester monomer. An electrostatic charge image developing carrier is provided.

  According to the fourth aspect of the present invention, compared to the case where the surface layer does not have the cross-linked structure, a change in print density at the beginning of the use of the developer is suppressed, and long-term image formation under low temperature and low humidity. Later, there is provided a developer for developing an electrostatic image in which image defects are suppressed while ensuring a stable print density.

  According to the invention of claim 5, the toner has an image after long-term image formation under low temperature and low humidity as compared with the case where the toner does not have external additive particles having a volume average particle diameter of 50 nm or more and 200 nm or less. Provided is a developer for developing an electrostatic image in which defects are further suppressed.

  According to the sixth aspect of the present invention, compared to the case where the surface layer does not have the cross-linked structure, a change in print density at the beginning of the use of the developer is suppressed, and long-term image formation under low temperature and low humidity. Later, a developer cartridge containing a developer for developing an electrostatic charge image in which image defects are suppressed while ensuring a stable print density is provided.

  According to the invention of claim 7, compared to the case where the surface layer does not have the cross-linked structure, the change in the print density at the beginning of the use of the developer is suppressed, and long-term image formation under low temperature and low humidity. Later, there is provided a process cartridge containing a developer for developing an electrostatic image in which image defects are suppressed while ensuring a stable print density.

  According to the eighth aspect of the present invention, compared to the case where the surface layer does not have the cross-linked structure, a change in print density at the beginning of the use of the developer is suppressed, and long-term image formation under low temperature and low humidity. There is provided an image forming apparatus capable of suppressing image defects while ensuring a stable print density.

1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an embodiment of the present invention. It is a schematic block diagram which shows the other example of the image forming apparatus which concerns on embodiment of this invention. It is a schematic structure figure showing an example of a process cartridge concerning an embodiment of the present invention.

  Embodiments of the present invention will be described below. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.

<Carrier for developing electrostatic image>
The electrostatic charge image developing carrier according to the exemplary embodiment includes a magnetic core material particle having a resin coating layer, and a resin including a monomer unit having a carboxy group in the coating resin included in the resin coating layer. Since the surface layer of the coating layer has a structure in which the carboxy group is crosslinked with a metal having a valence of 2 or more (hereinafter also simply referred to as “crosslinked structure”), the surface layer has the crosslinked structure. Compared with the case where the developer is not used, the change in the print density at the beginning of the use of the developer is suppressed, and even after long-term image formation under low temperature and low humidity, image defects are suppressed while ensuring a stable print density. .

  With the increase in printing speed by electrophotography and the diversification of the usage environment, it is desirable that the carrier having a resin coating layer has less variation in surface composition and structure over a long period of time. However, if the developer is used for a long period of time, the composition may vary due to the adhesion of the additive contained in the developer toner to the carrier surface, and the charge amount of the carrier may vary. Such a composition variation may appear remarkably at the beginning of the use of the developer. Also, in image formation after long-term continuous use under low temperature and low humidity, the charge amount of the carrier increases, and the scattered toner contaminates or damages the charging roll, the photosensitive member, the photosensitive member cleaning member, etc., and the image becomes dirty. An image defect may occur. “Initial start of use of developer” means immediately after the start of use of a new developer, and is not particularly limited. For example, printing is newly started using a developer. After that, it means a period of about 1000 printed on A4 paper.

  As a result of earnest research, the present inventor has at least magnetic core particles and a resin coating layer covering the magnetic core particles, and the resin coating layer contains a resin containing a monomer unit having a carboxy group. And when the surface layer of the resin coating layer has a cross-linked structure between a carboxy group contained in the resin and a metal having a valence of 2 or more, the surface layer does not have the cross-linked structure. In comparison, the change in print density at the beginning of the use of the developer is suppressed, and even after long-term image formation under low temperature and low humidity, the occurrence of image defects is suppressed while ensuring a stable print density. I found out. This has a structure containing a carboxy group as a coating resin, thereby suppressing an increase in chargeability in a low-temperature and low-humidity environment, and further containing a metal having a valence of 2 or more on the surface. Charge fluctuation at the beginning of use can be suppressed, and the surface layer can be adjusted to maintain the suppression effect by cross-linking a metal having a valence of 2 or more and a carboxy group, and stable chargeability In addition, a stable toner charge amount can be obtained over a long period of time even in a low temperature and low humidity environment. This is considered to be because image defects such as a decrease in reproducibility of the image are suppressed.

  In the electrostatic charge image developing carrier according to the exemplary embodiment, “the surface layer of the resin coating layer has the crosslinked structure” means that the surface layer of the resin coating layer includes a carboxy group and an atom contained in the resin. It represents that it has a cross-linking structure with a metal having a valence of 2 or more, and the portion other than the surface layer of the resin coating layer has substantially no cross-linking structure. The inventors of the present invention have found the above advantages by having the cross-linked structure in the surface layer of the resin coating layer, and when the resin coating layer other than the surface layer has the cross-linked structure, As a result, the surface of the resin coating layer is abraded, resulting in a refreshing effect that eliminates contamination on the carrier surface together with the shaved coating resin, resulting in reduced chargeability after long-term image formation and printing. It has also been found that print quality such as density and image defects may be deteriorated. Therefore, the electrostatic charge image developing carrier according to the present embodiment has the cross-linked structure on the surface layer of the resin coating layer, and the cross-linked structure is substantially not included in the portion other than the surface layer of the resin coating layer. As a non-contained material, only the surface layer of the resin coating layer has the crosslinked structure.

  Here, “the portion other than the surface layer of the resin coating layer has substantially no cross-linking structure” means that the layer thickness of the resin coating layer from the carrier surface in the metal cross-linking structure quantification method described later. It means that only less than 5% of the metal cross-linking structure is included in the range exceeding 10%.

  Hereinafter, the configuration of the carrier according to the present embodiment will be described.

  Examples of the magnetic core particle generally include a magnetic metal, a magnetic oxide, or a resin particle in which magnetic particles are dispersed internally. However, since these are hydrophilic and the chargeability may decrease under high humidity, the environmental fluctuation of the chargeability may increase. In addition, since it is a high surface energy material, it is easily contaminated with toner components, and the chargeability may be poorly maintained. Therefore, the carrier in the present embodiment is a resin-coated carrier having a resin coating layer in which the surface of the magnetic core particles is coated with a coating resin having hydrophobicity or low surface energy. This improves the above-mentioned problems relating to charging. In the present specification, a resin-coated carrier for developing an electrostatic charge image containing at least magnetic core particles and a resin coating layer covering the surfaces of the magnetic core particles is also simply referred to as “carrier”.

  In the resin coating process in which the resin coating layer is formed on the surface of the magnetic core particles, a typical method includes a wet method using a solvent and a dry method using no solvent.

  As a wet method, a resin for coating layer formation and a conductive material or the like as necessary are prepared in a solvent that is soluble in the resin to prepare a coating layer forming solution. Immersion method in which the coating layer forming solution is immersed, spray method in which the coating layer forming solution is sprayed on the surface of the magnetic core particle, and the coating layer forming state in which the magnetic core particle is suspended by flowing air or the like The coating material for forming the coating layer is applied to the magnetic core particles by a fluidized bed method in which the solution is sprayed, the magnetic core material particles and the coating layer forming solution are mixed in a kneader coater, and then the solvent is removed. There is a method of coating.

  As the dry method, the particles of the resin for forming a coating layer are synthesized by an emulsion polymerization method or a suspension polymerization method, or the resin for forming a coating layer synthesized by a conventional method is pulverized or dispersed in water. Then, the particles are mixed with the magnetic core particles, and the resin particles are fixed to the surface of the magnetic core particles by a mechanical impact force. There is a method in which a coating layer is formed by heating and melting above the glass transition point. In the present embodiment, when the coating layer is formed using a resin for crosslinking with a metal having a valence of 2 or more, the carboxy group is unevenly distributed on the particle surface, so that the metal surface is efficiently crosslinked on the particle surface. Therefore, it is desirable to form the resin coating layer by a dry method, in particular, a dry method in which resin particles obtained by polymerization and drying by emulsion polymerization are fixed and fixed on the surfaces of the magnetic core particles.

  The magnetic core particles used in the present embodiment are not particularly limited. For example, magnetic metal such as iron, steel, nickel and cobalt, magnetic metal oxide such as ferrite and magnetite, and magnetic particles inside Examples thereof include particles composed of a dispersed resin and the like. In this embodiment, a magnetic material is used, and the magnetic powder is used alone for the magnetic core particle, or the magnetic powder is made into particles and dispersed in a resin.

  The volume average particle diameter of the magnetic core particles is preferably 20 μm or more and 100 μm or less. If the volume average particle size of the magnetic core particles is less than 20 μm, it may be easily developed together with the toner when used as a carrier, and if it exceeds 100 μm, the toner may be uniformly charged when used as a carrier. It becomes difficult and the chargeability of individual toners may differ greatly.

  The resin coating layer used in the present embodiment contains a resin having a monomer unit containing a carboxy group in the surface layer (hereinafter also referred to as “carboxy group-containing resin”). The carboxy group-containing resin includes a monomer unit containing a carboxy group derived from the monomer (hereinafter, also referred to as “carboxy group-containing monomer unit”) obtained by polymerization using a monomer containing a carboxy group. It has a structure. In the present embodiment, the “surface layer” of the resin coating layer indicates a range from the carrier surface to 10% of the layer thickness of the resin coating layer in a carrier obtained by coating magnetic core particles with a coating resin. .

  The monomer containing a carboxy group is not particularly limited as long as it is a monomer having a polymerizable structure. Specific examples of the carboxy group-containing resin include a monomer containing a carboxy group, preferably a carboxy group and a non-carboxy group. Oligomers or polymers obtained by polymerizing monomers containing both saturated ethylene groups alone, copolymer resins of the monomers and other monomers copolymerizable with the monomers, and salts thereof Is mentioned.

  As the monomer containing a carboxy group and an unsaturated ethylene group, any monomer containing at least one carboxy group and at least one unsaturated ethylene group can be used. And α, β-ethylenically unsaturated compounds having Examples of the α, β-ethylenically unsaturated compound having a carboxy group include acrylic acid, methacrylic acid, fumaric acid, maleic acid, itaconic acid, cinnamic acid, monomethyl maleate, monobutyl maleate, and monoester maleate. An octyl ester etc. and those salts are mentioned. Among these monomers, acrylic acid and methacrylic acid are preferable. These may be used alone or in combination of two or more.

  In the present specification, the term “oligomer” is not particularly limited when not specifically mentioned, but means that it is in the range of about 2 or more and less than 100 monomer units, and “polymer” without any particular mention. Is described, it means that the number of monomer units is 100 or more.

  The copolymer resin used as the carboxy group-containing resin in the surface layer of the resin coating layer is not particularly limited, but includes the monomer containing the carboxy group and the unsaturated ethylene group, and the unsaturated ethylene group. A copolymer resin with another monomer copolymerizable with the above monomer is preferable.

  As the other monomer, any compound that contains an unsaturated ethylene group and does not contain a carboxy group can be used. For example, a styrene monomer, a (meth) acrylic acid ester monomer, a vinyl ester monomer, Alkenes etc. are mentioned. Examples of the styrene monomer include styrene, α-methylstyrene, 4-methylstyrene, and the like. Examples of the (meth) acrylic acid ester monomer include an alicyclic (meth) acrylic acid ester which is an ester compound of an alicyclic hydrocarbon having an alcoholic hydroxyl group and (meth) acrylic acid, and an alcoholic hydroxyl group. Examples include aliphatic (meth) acrylic acid esters which are ester compounds of linear or branched aliphatic hydrocarbons and (meth) acrylic acid. Examples of the alicyclic (meth) acrylic acid ester include cyclohexyl methacrylate and cyclohexyl acrylate. Examples of the aliphatic (meth) acrylic acid ester include methyl (meth) acrylate and ethyl (meth) acrylate. Can be mentioned. The vinyl ester is an ester of vinyl alcohol and an organic acid, and examples thereof include vinyl acetate, vinyl benzoate, and vinyl propionate. Examples of the alkene include ethylene, propylene, butene, and butadiene. These may be used alone or in combination of two or more.

  In this specification, when “(meth) acrylic acid” is described, it means one or both of acrylic acid and methacrylic acid. The same applies to “(meth) acrylate”.

  The carboxy group-containing resin is preferably a copolymer resin obtained by copolymerizing a monomer containing a carboxy group and an unsaturated ethylene group with a styrene compound or a (meth) acrylic acid ester monomer. A copolymer resin obtained by polymerizing a monomer containing a saturated ethylene group and a (meth) acrylate monomer is more preferred. This is because the characteristics of the resulting resin coating layer can be controlled by the copolymerization composition, and therefore, the charge controllability of the carrier by changing the copolymerization composition is excellent.

  Furthermore, as the carboxy group-containing resin, a copolymer obtained by using a monomer containing a carboxy group and an unsaturated ethylene group and an alicyclic (meth) acrylate monomer as the (meth) acrylate monomer A resin is more preferable. This is because the hygroscopicity of the resulting resin coating layer is lowered, and carrier characteristic fluctuations due to the temperature and humidity environment used are reduced. Specific examples of the alicyclic (meth) acrylic acid ester monomer include aliphatic cyclic hydrocarbon (meth) acrylic acid esters having 3 to 13 carbon atoms, preferably 5 to 10 carbon atoms. (Meth) acrylic acid esters of aliphatic cyclic hydrocarbons. Examples of the alicyclic (meth) acrylic acid ester monomer include cyclohexyl methacrylate and isobornyl acrylate.

  In the surface layer of the resin coating layer, in addition to the carboxy group-containing resin, other resins may be included. Other resins that may be included in the surface layer include, for example, polyethylene, polypropylene, polystyrene, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether, polyvinyl ketone, poly Acrylic ester, vinyl chloride-vinyl acetate copolymer, fluororesin, polyester, polyurethane, polycarbonate, phenol resin, amino resin, melamine resin, benzoguanamine resin, urea resin, amide resin, epoxy resin, etc. It is not limited.

  The content of the carboxy group-containing monomer unit contained in the resin constituting the resin coating layer is preferably 0.1% by mass or more and 30% by mass or less with respect to the total amount of the coating resin contained in the surface layer. 5 mass% or more and 5 mass% or less are more preferable. When the content is less than 0.1% by mass, a crosslinking reaction with a metal having a valence of 2 or more may not occur, and the effect of suppressing an increase in chargeability of the carrier may be reduced. When the content is 30% by mass or more, the hygroscopicity is increased, and the charging ability of the carrier when printing in a high humidity environment may be reduced.

  The content of the carboxy group-containing monomer unit contained in the resin constituting the resin coating layer is, for example, the type of the monomer containing the carboxy group and the unsaturated ethylene group, when producing the copolymer resin, The amount is adjusted according to the type and amount of other copolymerizable monomers and the type and content of other resins that may be contained in the surface layer of the resin coating layer.

  As a method for measuring the content of the carboxy group-containing monomer in the carrier coating resin of the present embodiment, 5 g of carrier and 50 g of chloroform are placed in a beaker, and the coating resin is sufficiently dissolved by an ultrasonic dispersing machine. After drying the coating resin extract from which insoluble matter such as powder has been separated by filtration to obtain a coating resin, 20 mg of the recovered coating resin is dissolved in 10 ml of chloroform, filtered, and then subjected to measurement by infrared absorption spectrum analysis. There is a way to ask.

  Moreover, there exists a nuclear magnetic resonance method (NMR) as a method of analyzing the monomer structural unit which comprises the coating resin of the carrier of this embodiment, and measuring content of the carboxy-group containing monomer in coating resin.

  In the present embodiment, when the magnetic core particles are coated with a coating resin, it is preferable to prepare the resin particles of the coating resin and fix the resin particles to the magnetic core particles by the dry method. The average particle size of the resin particles at this time is usually 3 μm (3 μm or less) at most, and preferably 10 nm or more and 1000 nm or less. If the average particle diameter exceeds 3 μm, the thickness of the coating resin layer of the finally obtained carrier cannot be precisely controlled, and problems such as a decrease in dispersibility of other additives occur, resulting in performance and It tends to cause a decrease in reliability. On the other hand, when the average particle size is within the above range, there are no disadvantages, and it is advantageous in that uneven distribution of the composition in the carrier coating resin layer is reduced, and variations in performance and reliability are reduced. The average particle diameter is measured using, for example, a microtrack.

  In the present embodiment, when the particles of the coating resin are prepared, it is possible to prepare particles having a small individual difference in particle diameter, and it is possible to localize carboxy groups on the surface of the resin particles. The resin particles are preferably synthesized by an emulsion polymerization method. In this embodiment, the resin particles are synthesized by emulsion polymerization, for example, in an aqueous solution containing a surfactant (emulsifier), the carboxy group and the ethylenically unsaturated group-containing monomer, and, if necessary, other ethylenic monomers. An unsaturated group-containing monomer and a chain transfer agent are added to form an emulsion, and then a water-soluble radical polymerization initiator is added to advance the polymerization reaction.

  The radical polymerization initiator used in carrying out the emulsion polymerization in the present embodiment is not particularly limited as long as it is a radical polymerization initiator usually used for emulsion polymerization. Specifically, for example, hydrogen peroxide, acetyl peroxide, cumyl peroxide, tert-butyl peroxide, propionyl peroxide, benzoyl peroxide, chlorobenzoyl peroxide, dichlorobenzoyl peroxide, bromomethylbenzoyl peroxide, Lauroyl oxide, ammonium persulfate, sodium persulfate, potassium persulfate, diisopropyl peroxycarbonate, tetralin hydroperoxide, 1-phenyl-2-methylpropyl-1-hydroperoxide, pertriphenylacetic acid tert-butyl hydroperoxide, formic acid tert- Peroxides such as butyl, tert-butyl peracetate, tert-butyl perbenzoate, tert-butyl perphenylacetate, tert-butyl permethoxyacetate, tert-butyl perN- (3-toluyl) carbamate; 2 , 2'-a Bispropane, 2,2′-dichloro-2,2′-azobispropane, 1,1′-azo (methylethyl) diacetate, 2,2′-azobis (2-amidinopropane) hydrochloride, 2,2 '-Azobis (2-amidinopropane) nitrate, 2,2'-azobisisobutane, 2,2'-azobisisobutyramide, 2,2'-azobisisobutyronitrile, 2,2'-azobis-2 -Methyl methyl propionate, 2,2'-dichloro-2,2'-azobisbutane, 2,2'-azobis-2-methylbutyronitrile, dimethyl 2,2'-azobisisobutyrate, 1,1'-azobis ( 1-methylbutyronitrile-3-sodium sulfonate), 2- (4-methylphenylazo) -2-methylmalonodinitrile, 4,4′-azobis-4-cyanovaleric acid, 3, -Dihydroxymethylphenylazo-2-methylmalonodinitrile, 2- (4-bromophenylazo) -2-allylmalonodinitrile, 2,2'-azobis-2-methylvaleronitrile, 4,4'-azobis- Dimethyl 4-cyanovalerate, 2,2′-azobis-2,4-dimethylvaleronitrile, 1,1′-azobiscyclohexanenitrile, 2,2′-azobis-2-propylbutyronitrile, 1,1 ′ -Azobis-1-chlorophenylethane, 1,1'-azobis-1-cyclohexanecarbonitrile, 1,1'-azobis-1-cycloheptanenitrile, 1,1'-azobis-1-phenylethane, 1,1 '-Azobiscumene, 4-nitrophenylazobenzylcyanoacetate, phenylazodiphenylmethane, phenylazotrif Phenylmethane, 4-nitrophenylazotriphenylmethane, 1,1′-azobis-1,2-diphenylethane, poly (bisphenol A-4,4′-azobis-4-cyanopentanoate), poly (tetraethylene glycol) Azo compounds such as -2,2'-azobisisobutyrate); 1,4-bis (pentaethylene) -2-tetrazene, 1,4-dimethoxycarbonyl-1,4-diphenyl-2-tetrazene and the like Can be mentioned.

  In the present embodiment, when the particles of the coating resin are prepared by emulsion polymerization, the molecular weight of the coating resin may be adjusted using a chain transfer agent. The chain transfer agent used when emulsification polymerization is carried out in the present embodiment is not particularly limited, and specifically, one having a covalent bond between a carbon atom and a sulfur atom is preferable, and more specifically, N-alkyl mercaptans such as n-propyl mercaptan, n-butyl mercaptan, n-amyl mercaptan, n-hexyl mercaptan, n-heptyl mercaptan, n-octyl mercaptan, n-nonyl mercaptan, n-decyl mercaptan; , Isobutyl mercaptan, s-butyl mercaptan, tert-butyl mercaptan, cyclohexyl mercaptan, tert-hexadecyl mercaptan, tert-lauryl mercaptan, tert-nonyl mercaptan, tert-octyl mercaptan, tert Branched alkyl mercaptans such as tetradecyl mercaptan; allyl mercaptan, 3-phenylpropyl mercaptan, phenyl mercaptan, mercaptans 含芳 incense ring system such as mercapto triphenylmethane; and the like.

  Although it does not specifically limit as surfactant used when implementing emulsion polymerization in this embodiment, A cationic surfactant, an anionic surfactant, and a nonionic surfactant may be used individually by 1 type, or 2 types You may use the above together.

  Examples of the cationic surfactant include amine salt type and quaternary ammonium salt type. Specific examples include laurylamine hydrochloride, stearylamine hydrochloride, oleylamine acetate, stearylamine acetate, stearylaminopropylamineacetic acid. Amine salts such as salts; lauryltrimethylammonium chloride, dilauryldimethylammonium chloride, distearylammonium chloride, distearyldimethylammonium chloride, lauryldihydroxyethylmethylammonium chloride, oleylbispolyoxyethylenemethylammonium chloride, lauroylaminopropyldimethylethyl Ammonium etosulphate, lauroylaminopropyldimethylhydroxyethylammonium perchlorate, al Le benzene dimethylammonio mode chloride, quaternary ammonium salts such as alkyl trimethyl ammonium chloride; and the like.

  Specific examples of the anionic surfactant include fatty acid soaps such as potassium laurate, sodium oleate and sodium castor oil; sulfates such as octyl sulfate, lauryl sulfate, lauryl ether sulfate and nonyl phenyl ether sulfate; lauryl sulfonate , Dodecyl sulfonate, dodecyl benzene sulfonate, triisopropyl naphthalene sulfonate, dibutyl naphthalene sulfonate, etc. Sulfonates such as lauryl phosphate, isopropyl phosphate Phosphoric acid esters such as nonyl phenyl ether phosphate; dialkyl sodium sulfosuccinates, such as sodium dioctyl sulfosuccinate, sodium lauryl sulfosuccinate 2, polyoxyethylene sulfo sulfosuccinate salts such as succinic acid lauryl disodium; and the like.

  Specific examples of the nonionic surfactant include polyoxyethylene octyl ether, polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether and other alkyl ethers; Alkylphenyl ethers such as oxyethylene nonylphenyl ether; alkyl esters such as polyoxyethylene laurate, polyoxyethylene stearate, polyoxyethylene oleate; polyoxyethylene lauryl amino ether, polyoxyethylene stearyl amino ether, polyoxy Alkylamines such as ethylene oleyl amino ether, polyoxyethylene soybean amino ether, polyoxyethylene beef tallow amino ether; Alkyl amides such as xylethylene lauric acid amide, polyoxyethylene stearic acid amide, polyoxyethylene oleic acid amide; vegetable oil ethers such as polyoxyethylene castor oil ether, polyoxyethylene rapeseed oil ether; lauric acid diethanolamide, stearin Alkanolamides such as acid diethanolamide and oleic acid diethanolamide; sorbitan ester ethers such as polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate And the like.

  In the present embodiment, the content of the surfactant used when carrying out the emulsion polymerization is preferably 1000 ppm or more and 55000 ppm or less, and more preferably 5000 ppm or more and 20000 ppm or less, based on the entire coated resin particles. By setting the amount to more than 1000 ppm, resin particles having a desired particle diameter can be obtained, and by setting the amount to 55000 ppm or less, a rapid decrease in charge due to hygroscopicity can be suppressed.

  As a method for measuring the content of the surfactant in the coating resin of the carrier of this embodiment, 5 g of carrier and 50 g of chloroform are put in a beaker, and the coating resin is sufficiently dissolved by an ultrasonic dispersing machine, and the magnetic core material particles are dissolved from this solution. The surfactant can be extracted from a coating resin extract obtained by filtering and separating insolubles such as conductive powder, and then can be determined by high performance liquid chromatography analysis.

  In this embodiment, the coating resin contained other than the surface layer in the resin coating layer may be the carboxy group-containing resin, or may be another resin other than the carboxy group-containing resin, You may mix and use these. Other resins than carboxy group-containing resins include polyethylene, polypropylene, polystyrene, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether, polyvinyl ketone, polyacrylic acid ester, vinyl chloride. -Vinyl acetate copolymer, fluororesin, polyester, polyurethane, polycarbonate, phenol resin, amino resin, melamine resin, benzoguanamine resin, urea resin, amide resin, epoxy resin, etc., but are not limited thereto. .

  In this embodiment, the coating resin contained other than the surface layer of the resin coating layer is a copolymer of a monomer containing a carboxy group and an unsaturated ethylene group and a styrene compound or a (meth) acrylic acid ester monomer. A polymer or copolymer obtained by homopolymerization of a certain carboxy group-containing resin, styrene compound or (meth) acrylate monomer, or copolymerization with another copolymerizable monomer, and a mixture thereof, This is preferable because controllability is improved. Furthermore, the above carboxy group-containing resin, which is a copolymer of a monomer containing a carboxy group and an unsaturated ethylene group and an alicyclic (meth) acrylate ester, homopolymerization of an alicyclic (meth) acrylate ester, Alternatively, a polymer or copolymer obtained by copolymerization with other copolymerizable monomers, and a mixture thereof are preferable because of their low hygroscopicity.

  In the present embodiment, the coating resin contained in the resin coating layer preferably has a weight average molecular weight of 10,000 or more and 1,000,000 or less, and more preferably 50,000 or more and 500,000 or less. . If the weight average molecular weight is less than 10,000, sufficient strength may not be obtained, and if the weight average molecular weight exceeds 1,000,000, uniform coating may not be achieved.

  In the present embodiment, the surface layer of the resin coating layer contains a metal having a valence of 2 or more. A metal having a valence of 2 or more and a carboxy group in the carboxy group-containing resin form a crosslinked structure. Any metal having a valence of 2 or more can be used as long as the valence is 2 or more. For example, Mg, Ca, Sr, Ti, Zr, Cr, Mo, W, Fe, Ru, Metals such as Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, and Cd are preferable. These metals should be used in the form of metal compounds such as oxides, oxides, peroxides, halides, sulfates, sulfites, nitrates, nitrites, carbonates, hydroxides, cyanides, metal complexes, etc. it can.

  The cross-linked structure according to the present invention is a state in which a carboxy group is adsorbed or bonded by a force such as an intermolecular force, an ionic bond, or a chelate bond through a metal having a valence of 2 or more. The surface layer of the coating resin layer indicates a range from the carrier surface to 10% of the layer thickness of the resin coating layer in a carrier formed by coating magnetic core particles with a coating resin.

  The metal crosslinking structure contained in the surface layer of the resin coating layer has a content of carboxyl groups that are crosslinked among the entire carboxyl groups when the coating resin forming the surface layer is analyzed by infrared absorption spectroscopy. It is preferably 5% or more and 100% or less, and more preferably 50% or more and 100% or less. If the content is less than 5%, the effect of suppressing the charge fluctuation of the carrier may be reduced.

  The method for forming a crosslinked structure on the surface layer of the resin coating layer according to this embodiment is not particularly limited. For example, after coating the carboxy group-containing resin on the magnetic core particles by any method, the carrier and the metal are coated. A method of heating a metal having an ion or a chelate structure in water; a method of coating the particles of the carboxy group-containing resin on magnetic core particles, adding metal oxide particles or the like to the surface, and crosslinking by heating; A coating containing a carboxy group-containing resin in which metal particles are dispersed in the outermost layer by coating the magnetic core particles with a resin a plurality of times and coating only with a resin containing a carboxy group-containing resin and metal particles only at the end. A method of forming a layer and crosslinking by heating; In the present embodiment, a method is preferred in which the coating resin is coated on the magnetic core particles a plurality of times, a coating layer containing a carboxy group-containing resin in which metal particles are dispersed only in the outermost layer, and heated. When forming a metal crosslink on the surface layer by coating the coating resin multiple times, the metal crosslink is formed on the surface layer by adjusting the coating amount and the coating conditions of each coating layer. Produces a carrier in which the coating resin does not substantially contain a crosslinked structure. The heating means and heating conditions for forming the crosslinked structure in each of the above methods are not particularly limited as long as the crosslinked structure is formed by the metal to be used and the carboxy group and the resin does not decompose.

  The measurement method of the crosslinked structure in the coating resin of the carrier of the present embodiment is as follows. The carrier, zirconia beads, and water are mixed in a glass container, and stirred with a ball mill while checking the thickness of the resin coating layer. When the layer thickness of the resin coating layer is polished by 10% or more, the zirconia beads and water are removed, and the carrier is dried. Each of 5 g of the obtained carrier and 5 g of the carrier before treatment and 50 g of chloroform are put in a beaker, and the coating resin is sufficiently dissolved with an ultrasonic disperser. Next, the coating resin extract from which insoluble components such as magnetic core particles and conductive powder are separated by filtration is dried to obtain a coating resin. After 20 mg of the recovered coating resin is dissolved in 10 ml of chloroform and filtered, the presence or absence of metal crosslinking can be determined by analyzing the solution by infrared absorption spectrum analysis. The content of the metal crosslinked structure in the coating resin is determined by analyzing the infrared absorption spectrum of the coating resin, and the COOM group (M is a metal having a valence of 2 or more) corresponding to the metal crosslinked structure. The concentration can be obtained.

  The resin coating layer in the carrier according to the embodiment of the present application may be added with a charge control agent, a conductive material, resin particles, and the like as necessary. If the surface of the core particle is coated with the coating resin at a high coverage, the electrical resistance as a carrier increases, and the reproducibility of a solid image may deteriorate. For this reason, it is preferable to disperse a charge control agent, a conductive material or the like in the resin coating layer in order to avoid an increase in electric resistance.

  In the carrier according to this embodiment, examples of the charge control agent that may be contained in the resin coating layer include nigrosine dyes, benzimidazole compounds, quaternary ammonium salt compounds, alkoxylated amines, alkylamides, and molybdate chelate pigments. , Triphenylmethane compounds, salicylic acid metal salt complexes, azo chromium complexes, copper phthalocyanines, and the like may be used. Particularly preferred are quaternary ammonium salt compounds, alkoxylated amines and alkylamides.

  The addition amount of the charge control agent used in the present embodiment is preferably 0.001 part by mass or more and 5 parts by mass or less, and 0.01 part by mass or more and 0.5 part by mass with respect to 100 parts by mass of the magnetic core particles. Part or less is more preferable. When the addition amount of the charge control agent exceeds 5 parts by mass, the strength of the resin coating layer is lowered, and the carrier may be easily deteriorated due to stress during use. When the addition amount of the charge control agent is less than 0.001 part by mass, not only the function of the charge control agent is not exhibited, but also the dispersibility of the conductive material may not be improved.

  Moreover, it is preferable to add resin particles to the resin coating layer in order to suppress a decrease in charge. Although it does not specifically limit as resin particle to be used, The particle | grains containing a nitrogen element are preferable. Of these, urea resins, urethane resins, melamine resins, guanamine resins, and amide resins are preferable because they have high positive chargeability and high resin hardness, so that a decrease in charge amount due to peeling of the resin coating layer is suppressed. The addition amount of the resin particles to be used is preferably 0.01 parts by mass or more and 5 parts by mass or less, and more preferably 0.1 parts by mass or more and 0.5 parts by mass or less with respect to 100 parts by mass of the magnetic core particles. . When the addition amount of the resin particles exceeds 5 parts by mass, the strength of the resin coating layer is lowered, and the carrier may be easily changed by stress during use. When the addition amount of the resin particles is less than 0.01 parts by mass, the function of suppressing the decrease in charge amount may not be exhibited.

  As the conductive material that may be added to the resin coating layer in the present embodiment, metals such as gold, silver, copper, titanium oxide, zinc oxide, tin oxide, barium sulfate, aluminum borate, potassium titanate, tin oxide, Examples thereof include tin oxide doped with antimony, indium oxide doped with tin, zinc oxide doped with aluminum, resin particles coated with metal, and carbon black.

  The content of the conductive material is preferably 0.01 parts by mass or more and 10 parts by mass or less, and 0.05 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the coating resin in order to make the carrier volume specific resistance a desired characteristic. Is more preferable. It is preferable that the content of the conductive material is 0.01 parts by mass or more because a resistance adjusting effect is obtained. Moreover, since it becomes difficult to detach | leave a conductive material as content is 10 mass parts or less, it is preferable.

  The average film thickness of the resin coating layer is, for example, 0.1 μm or more and 10 μm or less, but is preferably 0.5 μm or more and 3 μm or less in order to develop a stable volume resistivity of the carrier over time.

In order to achieve high image quality, the volume specific resistance value of the carrier according to the present embodiment is 1,000 V corresponding to the upper and lower limits of a normal development contrast potential, which is 10 ⁶ Ω · cm or more and 10 ¹⁴ Ω · It is preferably cm or less, and more preferably 10 ⁸ Ω · cm or more and 10 ¹³ Ω · cm or less. If the volume specific resistance value of the carrier is less than 10 ⁶ Ω · cm, the reproducibility of fine lines is poor, and the amount of carrier transferred to the photoconductor (image carrier) increases, which may easily damage the photoconductor. . On the other hand, if the volume resistivity of the carrier exceeds 10 ¹⁴ Ω · cm, reproduction of a black solid image or a halftone image may be deteriorated.

  The volume average particle size of the carrier according to this embodiment is preferably 20 μm or more and 100 μm or less. If the volume average particle diameter of the carrier is less than 20 μm, it may be easily developed together with the toner. If the carrier average particle diameter exceeds 100 μm, it becomes difficult to charge the toner substantially uniformly, and the chargeability of each toner is greatly different. May end up.

<Developer for developing electrostatic image>
The developer for developing an electrostatic charge image (developer) according to the present embodiment contains the carrier for developing an electrostatic charge image (carrier) and the toner for developing an electrostatic charge image (toner) according to the present embodiment. The developer according to this embodiment is prepared by mixing the carrier and toner according to this embodiment at an appropriate blending ratio. The carrier content ((carrier) / (carrier + toner) × 100) is preferably in the range of 85 to 99% by mass, more preferably in the range of 87 to 98% by mass, and 89% by mass or more. The range of 97% by mass or less is more preferable.

  Hereinafter, the toner used in the developer for developing an electrostatic charge image according to the exemplary embodiment will be described.

  The toner used in this embodiment contains at least a binder resin and a colorant, and if necessary, a release agent and other components. In addition to the toner particles having the above-described configuration, an external additive (hereinafter sometimes simply referred to as “external additive”) may be added to the toner used in the exemplary embodiment for various purposes. .

  For the toner used in this embodiment, a known binder resin, various colorants, and the like may be used. As the binder resin in the toner used in this embodiment, in addition to the polyester resin, polyolefin resin, copolymer of styrene and acrylic acid or methacrylic acid, polyvinyl chloride, phenol resin, acrylic resin, methacrylic resin, poly Vinyl acetate, silicone resin, modified polyester resin, polyurethane, polyamide resin, furan resin, epoxy resin, xylene resin, polyvinyl butyral, terpene resin, coumarone indene resin, petroleum resin, polyether polyol resin, etc. may be used alone You may use together.

  Examples of the colorant in the toner used in the exemplary embodiment include cyan colorants such as C.I. I. Pigment Blue 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 13, 15, 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 16, 17, 17, 23, 60, 65, 73, 83, 180, C.I. I. Vat cyan 1, 3 and 20, etc., bitumen, cobalt blue, alkali blue lake, phthalocyanine blue, metal-free phthalocyanine blue, partially chlorinated phthalocyanine blue, first sky blue, indanthrene blue BC cyan pigment, C.I. I. Cyan dyes such as solvent cyan 79 and 162 may be used.

  Examples of magenta colorants include C.I. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 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, 184, 202, 206, 207, and 209, pigment violet 19 magenta pigments, C.I. I. Solvent Red 1, 3, 8, 23, 24, 25, 27, 30, 30, 49, 81, 82, 83, 84, 100, 109, 121, C . I. Disper thread 9, C.I. I. Basic Red 1, 2, 9, 9, 13, 14, 15, 17, 17, 18, 22, 23, 24, 27, 29, 32, 34, the same 35, 36, 37, 38, 39, 40, etc. Magenta dyes, etc., Bengala, Cadmium Red, Lead Tan, Mercury Sulfide, Cadmium, Permanent Red 4R, Resol Red, Pyrazolone Red, Watching Red, Calcium Salt, lake red D, brilliant carmine 6B, eosin lake, rotamin lake B, alizarin lake, brilliant carmine 3B and the like may be used.

  Examples of yellow colorants include C.I. I. Pigment Yellow 2, 3, 15, 15, 16, 17, 97, 180, 185, 139, and the like may be used.

  Further, in the case of black toner, for example, carbon black, activated carbon, titanium black, magnetic powder, Mn-containing nonmagnetic powder, or the like may be used.

  The toner used in the exemplary embodiment may contain a charge control agent, and nigrosine, a quaternary ammonium salt, an organometallic complex, a chelate complex, or the like may be used.

Further, in this embodiment, various resin powders and inorganic compounds are added as surface modifiers to the surface of the toner particles as particulate external additives (also referred to as “external additive particles” in this specification). May be. Among the external additive particles, as the resin powder, spherical particles such as polymethyl methacrylate resin (PMMA), nylon, melamine, benzoguanamine, and fluorine resin can be used. Among the external additive particles, various known inorganic compounds include, for example, SiO ₂ , TiO ₂ , Al ₂ O ₃ , MgO, CuO, ZnO, SnO ₂ , CeO ₂ , Fe ₂ O ₃ , BaO, CaO, Examples include K ₂ O, Na ₂ O, ZrO ₂ , CaO · SiO ₂ , CaCO ₃ , K ₂ O (TiO ₂ ) _n , MgCO ₃ , Al ₂ O ₃ · 2SiO ₂ , BaSO ₄ , MgSO _{4 and the} like. Preferably, SiO ₂ , TiO ₂ , and Al ₂ O ₃ can be used, but the present invention is not limited to these, and one or more of these may be used in combination. The amount of the external additive particles added is, for example, in the range of 0.1% by mass to 20% by mass with respect to 100% by mass of the toner particles.

  In the present embodiment, it is desirable to use the toner to which the external additive particles are added in order to obtain a stable print quality over a long period of time. In this embodiment, the volume average particle diameter is 50 nm or more and 200 nm or less. Use of the toner for developing an electrostatic charge image having additive particles is particularly preferable from the viewpoint of embedding and deformation of the surface of the carrier of this embodiment, and an appropriate polishing suppression effect, and an external additive having a volume average particle size of 80 nm or more and 150 nm or less. It is more preferable to use a toner for developing an electrostatic image having agent particles. When the volume average particle size of the external additive particles is less than 50 nm, the appropriate polishing effect on the surface of the carrier may be impaired, and when the volume average particle size of the external additive particles exceeds 200 nm, the adhesion to the toner May not be obtained.

  Furthermore, the toner used in the exemplary embodiment preferably contains a release agent. Examples of the release agent include ester wax, polyethylene, polypropylene, or a copolymer of polyethylene and polypropylene, polyglycerin wax, microcrystalline wax, paraffin wax, carnauba wax, sazol wax, montanic ester wax, deoxidized carnauba wax, and the like. Polymers and waxes; unsaturated fatty acids such as palmitic acid, stearic acid, montanic acid, brandic acid, eleostearic acid, valinalic acid; stearic alcohol, aralkyl alcohol, behenyl alcohol, carnauvyl alcohol, seryl alcohol, melyl alcohol Or a saturated alcohol such as a long-chain alkyl alcohol having a long-chain alkyl group; a polyhydric alcohol such as sorbitol; a linoleic acid amide, Fatty acid amides such as inamide, lauric acid amide; saturated fatty acid bisamides such as methylenebisstearic acid amide, ethylene biscapric acid amide, ethylene bislauric acid amide, hexamethylene bisstearic acid amide, ethylene bisoleic acid amide, Unsaturated fatty acid amides such as hexamethylenebisoleic acid amide, N, N′-dioleyl adipic acid amide, N, N′-dioleyl sebacic acid amide; m-xylene bisstearic acid amide, N, N′di Aromatic bisamides such as stearyl isophthalic acid amide; fatty acid metal salts such as calcium stearate, calcium laurate, zinc stearate, magnesium stearate (generally referred to as metal soap); aliphatic hydrocarbon wax with styrene or Acrylic acid Waxes grafted with other vinyl monomers; partially esterified products of fatty acids such as behenic monoglyceride and polyhydric alcohols; methyl ester compounds having hydroxyl groups obtained by hydrogenation of vegetable oils and the like .

  In this embodiment, the method for producing the toner (toner particles) is not particularly limited, but it is preferably produced by a wet production method in order to obtain high image quality. As a wet manufacturing method, the polymerizable monomer of the binder resin is emulsion-polymerized, and the formed binder resin dispersion is mixed with a dispersion of a colorant, a release agent, and, if necessary, a charge control agent. An emulsion aggregation method in which toner particles are obtained by agglomeration and heat fusion; a solution of a polymerizable monomer and a colorant, a release agent, and a charge control agent as required in order to obtain a binder resin in an aqueous solvent Suspension polymerization method in which the polymer is suspended and polymerized; a suspension method in which a binder resin, a colorant, a release agent, and a charge control agent, if necessary, are suspended in an aqueous solvent and granulated; etc. Is mentioned. In addition, a manufacturing method may be performed in which the toner particles obtained by the above method are used as a core, and resin particles are further adhered and heat-fused to have a core-shell structure. Further, toner particles obtained by a general pulverization classification method may be used.

<Image Forming Apparatus, Image Forming Method, and Process Cartridge>
The image forming apparatus according to the exemplary embodiment includes an image carrier, a charging unit that charges the surface of the image carrier, an electrostatic image forming unit that forms an electrostatic image on the surface of the image carrier, and the electrostatic image. Is developed with the electrostatic charge image developing developer according to the present embodiment to form a toner image, and a transfer means for transferring the toner image to a recording medium. The image forming apparatus according to the present embodiment may include a fixing unit that fixes the toner image on the recording medium, an image carrier cleaning unit that cleans the surface of the image carrier, and the like, as necessary.

  In this image forming apparatus, for example, the part including the developing unit may have a cartridge structure (process cartridge) that can be attached to and detached from the main body of the image forming apparatus. The process cartridge contains the developer for developing an electrostatic image according to the present embodiment, and the electrostatic image formed on the surface of the image carrier is developed with the developer for developing the electrostatic image to form a toner image. A process cartridge that includes a developing unit that is attached to and detached from the image forming apparatus is preferably used. This facilitates the handling of the developer for developing an electrostatic image, and enhances the adaptability to image forming apparatuses having various configurations.

  The image forming apparatus according to the present embodiment uses the charging process for charging the surface of the image carrier, the electrostatic charge image forming process for forming an electrostatic charge image on the surface of the image carrier, and the electrostatic charge image according to the present embodiment. A book including a developing step of developing with a developer for developing an electrostatic image to form a toner image, a transferring step of transferring the toner image to a recording medium, and a fixing step of fixing the toner image on the recording medium. The image forming method according to the embodiment is performed.

  Hereinafter, an example of the image forming apparatus according to the present embodiment will be described, but the present invention is not limited thereto.

  FIG. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to the present embodiment. The image forming apparatus 301 includes a charging unit 310, an exposure unit 312, an electrophotographic photosensitive member 314 that is an image holding member, a developing unit 316, a transfer unit 318, a cleaning unit 320, and a fixing unit 322.

  In the image forming apparatus 301, around the electrophotographic photosensitive member 314, a charging unit 310 that is a charging unit that charges the surface of the electrophotographic photosensitive member 314 and the charged electrophotographic photosensitive member 314 are exposed according to image information. An exposure unit 312 that is an electrostatic image forming unit that forms an electrostatic image, a developing unit 316 that is a developing unit that develops the electrostatic image with a developer to form a toner image, and the surface of the electrophotographic photoreceptor 314 The transfer unit 318 that is a transfer unit that transfers the toner image formed on the surface of the recording medium 324 and foreign matters such as toner remaining on the surface of the electrophotographic photosensitive member 314 after the transfer are removed to remove the toner image. And a cleaning unit 320 which is an image carrier cleaning means for cleaning the surface of the lens is arranged in this order. A fixing unit 322 that is a fixing unit that fixes the toner image transferred to the recording medium 324 is disposed on the side of the transfer unit 318.

  The operation of the image forming apparatus 301 according to this embodiment will be described. First, the charging unit 310 charges the surface of the electrophotographic photosensitive member 314 that is an image holding member (charging step). Next, light is applied to the surface of the electrophotographic photosensitive member 314 by the exposure unit 312, and the charged charge in the exposed part is removed, and an electrostatic image is formed according to image information (electrostatic image formation). Process). Thereafter, the electrostatic charge image is developed by the developing unit 316, and a toner image is formed on the surface of the electrophotographic photosensitive member 314 (development process). For example, in the case of a digital electrophotographic copying machine using an organic photoconductor as the electrophotographic photoconductor 314 and using a laser beam as the exposure unit 312, the surface of the electrophotographic photoconductor 314 is negatively charged by the charging unit 310. Then, a digital electrostatic charge image is formed in a dot shape by the laser beam light, and toner is applied to a portion irradiated with the laser beam light by the developing unit 316 to be visualized. In this case, a negative bias is applied to the developing unit 316. Next, a recording medium 324 such as paper is superimposed on the toner image at the transfer unit 318, and a charge having a polarity opposite to that of the toner is applied to the recording medium 324 from the back side of the recording medium 324. 324 is transferred (transfer process). The transferred toner image is heated and pressed by a fixing member in the fixing unit 322, and is fused and fixed to the recording medium 324 (fixing step). On the other hand, foreign matters such as toner remaining on the surface of the electrophotographic photosensitive member 314 without being transferred are removed by the cleaning unit 320 (cleaning step). One cycle is completed in a series of processes from charging to cleaning. In FIG. 1, the toner image is directly transferred to the recording medium 324 such as paper by the transfer unit 318, but may be transferred via a transfer body such as an intermediate transfer body.

  Hereinafter, the charging unit, the image carrier, the electrostatic image forming unit (exposure unit), the developing unit, the transfer unit, the image carrier cleaning unit, and the fixing unit in the image forming apparatus 301 of FIG. 1 will be described.

(Charging means)
As the charging unit 310 serving as a charging unit, for example, a charger such as a corotron shown in FIG. 1 is used, but a conductive or semiconductive charging roll may be used. A contact charger using a conductive or semiconductive charging roll may apply a direct current to the electrophotographic photosensitive member 314 or may apply an alternating current superimposed thereon. For example, the charging unit 310 charges the surface of the electrophotographic photosensitive member 314 by generating a discharge in a minute space near the contact portion with the electrophotographic photosensitive member 314. Usually, it is charged to −1000 V or more and −300 V or less. The conductive or semiconductive charging roll may have a single layer structure or a multiple structure. Further, a mechanism for cleaning the surface of the charging roll may be provided.

(Image carrier)
The image carrier has a function of forming at least an electrostatic charge image (latent image). As the image carrier, an electrophotographic photosensitive member is preferably exemplified. The electrophotographic photoreceptor 314 has a coating film containing an organic photoreceptor or the like on the outer peripheral surface of a cylindrical conductive substrate. The coating film is a substrate in which a subbing layer and a photosensitive layer including a charge generating layer containing a charge generating material and a charge transporting layer containing a charge transporting material are formed in this order, if necessary. is there. The order of stacking the charge generation layer and the charge transport layer may be reversed. These are laminated photoconductors in which a charge generation material and a charge transport material are contained in separate layers (charge generation layer, charge transport layer), but both the charge generation material and the charge transport material are the same. It may be a single layer type photoreceptor included in the above layer, and is preferably a laminated type photoreceptor. Further, an intermediate layer may be provided between the undercoat layer and the photosensitive layer. In addition, other types of photosensitive layers such as an amorphous silicon photosensitive film may be used in addition to the organic photoreceptor.

(Static charge image forming means)
The exposure unit 312 which is an electrostatic charge image forming unit (exposure unit) is not particularly limited, and for example, a light source such as a semiconductor laser beam, LED (Light Emitting Diode) light, or liquid crystal shutter light is provided on the surface of the image carrier. Examples thereof include an optical device that exposes a desired image.

(Development means)
The developing unit 316 serving as a developing unit has a function of developing the electrostatic charge image formed on the image carrier with a developer containing toner to form a toner image. The developing device is not particularly limited as long as it has the above-described function, and may be selected according to the purpose. And a known developing device having a function of adhering to the surface. The electrophotographic photosensitive member 314 normally uses a DC voltage, but may be used with an AC voltage superimposed thereon.

(Transfer means)
As the transfer unit 318 that is a transfer unit, for example, a charge opposite in polarity to the toner is applied to the recording medium 324 from the back side of the recording medium 324 shown in FIG. 1, and the toner image is transferred to the recording medium 324 by electrostatic force. Alternatively, a transfer roll and a transfer roll pressing device using a conductive or semiconductive roll that directly contacts and transfers to the recording medium 324 may be used. A direct current may be applied to the transfer roll as a transfer current applied to the image carrier, or an alternating current may be applied in a superimposed manner. The transfer roll may be set according to the image area width to be charged, the shape of the transfer charger, the opening width, the process speed (circumferential speed), and the like, as in the prior art. Further, a single layer foam roll or the like is suitably used as a transfer roll for cost reduction. As a transfer method, a method of directly transferring to a recording medium 324 such as paper or a method of transferring to a recording medium 324 via an intermediate transfer member may be used.

  A known intermediate transfer member may be used as the intermediate transfer member. Materials used for the intermediate transfer member include polycarbonate resin (PC), polyvinylidene fluoride (PVDF), polyalkylene phthalate, thermosetting polyimide resin; and PC / polyalkylene terephthalate (PAT), ethylene tetrafluoroethylene copolymer. Examples thereof include blend materials such as (ETFE) / PC and ETFE / PAT. From the viewpoint of mechanical strength, an intermediate transfer belt using a thermosetting polyimide resin is preferable.

(Image carrier cleaning means)
As for the cleaning unit 320 that is an image carrier cleaning means, a blade cleaning method, a brush cleaning method, a roll cleaning method, or the like may be selected as long as it cleans foreign matters such as residual toner on the image carrier. That's fine.

(Fixing means)
The fixing unit 322 as a fixing unit (image fixing device) fixes a toner image transferred to the recording medium 324 by heating, pressing, or heating and pressing, and includes a fixing member.

(recoding media)
Examples of the recording medium 324 to which the toner image is transferred include plain paper, an OHP sheet, and the like used for an electrophotographic copying machine or printer. In order to further improve the smoothness of the image surface after fixing, the surface of the recording medium is also preferably smooth. For example, coated paper with the surface of plain paper coated with resin, art paper for printing, etc. are used. May be.

  Further, by combining with trickle development proposed in Japanese Examined Patent Publication No. 2-21591, stable image formation can be achieved over a longer period.

  FIG. 2 is a schematic configuration diagram illustrating a quadruple tandem color image forming apparatus as another example of the image forming apparatus according to the present exemplary embodiment. The image forming apparatus shown in FIG. 2 is a first to first electrophotographic method that outputs yellow (Y), magenta (M), cyan (C), and black (K) images based on color-separated image data. Fourth image forming units 10Y, 10M, 10C, and 10K (image forming means) are provided. These image forming units (hereinafter sometimes simply referred to as “units”) 10Y, 10M, 10C, and 10K are installed side by side in a predetermined distance from each other in the horizontal direction. The units 10Y, 10M, 10C, and 10K may be process cartridges that can be attached to and detached from the image forming apparatus main body.

  Above each unit 10Y, 10M, 10C, and 10K in the drawing, an intermediate transfer belt 20 as an intermediate transfer member is provided to extend through each unit. The intermediate transfer belt 20 is provided by being wound around a driving roller 22 and a support roller 24 that are in contact with the inner surface of the intermediate transfer belt 20 arranged at a distance from the left to the right in the drawing. The vehicle travels in the direction toward the unit 10K. The support roller 24 is applied with a force in a direction away from the driving roller 22 by a spring or the like (not shown), and tension is applied to the intermediate transfer belt 20 wound around the both. Further, an intermediate transfer member cleaning device 30 is provided on the side of the image carrier of the intermediate transfer belt 20 so as to face the driving roller 22. Further, yellow, magenta, cyan, and black, which are housed in toner cartridges 8Y, 8M, 8C, and 8K, are respectively provided in the developing devices (developing units) 4Y, 4M, 4C, and 4K of the units 10Y, 10M, 10C, and 10K. The four colors of toner are supplied.

  Since the first to fourth units 10Y, 10M, 10C, and 10K described above have the same configuration, here, a first image that forms a yellow image disposed on the upstream side in the intermediate transfer belt traveling direction is formed. The unit 10Y will be described as a representative. It should be noted that reference numerals with magenta (M), cyan (C), and black (K) are attached to the same parts as those of the first unit 10Y instead of yellow (Y). The description of the units 10M, 10C, and 10K will be omitted.

  The first unit 10Y includes a photoreceptor 1Y that functions as an image holding member. Around the photosensitive member 1Y, a charging roller 2Y for charging the surface of the photosensitive member 1Y to a predetermined potential, and the charged surface is exposed by a laser beam 3Y based on the color-separated image signal to form an electrostatic charge image. An exposure device (electrostatic image forming means) 3 for forming, a developing device (developing means) 4Y for supplying the charged toner to the electrostatic image and developing the electrostatic image, and transferring the developed toner image onto the intermediate transfer belt 20 A primary transfer roller 5Y (primary transfer unit) that performs the transfer and a photoconductor cleaning device (cleaning unit) 6Y that removes toner remaining on the surface of the photoconductor 1Y after the primary transfer are sequentially arranged.

  The primary transfer roller 5Y is disposed inside the intermediate transfer belt 20 and is provided at a position facing the photoreceptor 1Y. Further, a bias power source (not shown) for applying a primary transfer bias is connected to each primary transfer roller 5Y (5M, 5C, 5K). Each bias power source varies the transfer bias applied to each primary transfer roller under the control of a control unit (not shown).

Hereinafter, an operation of forming a yellow image in the first unit 10Y will be described. First, prior to the operation, the surface of the photoreceptor 1Y is charged to a potential of about −800 V or more and −600 V or less by the charging roller 2Y. The photoreceptor 1Y is formed by laminating a photosensitive layer on a conductive substrate (for example, a volume resistivity at 20 ° C. is 1 × 10 ⁻⁶ Ωcm or less). This photosensitive layer usually has a high resistance (having a resistivity equivalent to that of a general resin), but has a property that the specific resistance of the portion irradiated with the laser beam changes when irradiated with the laser beam 3Y. ing. Therefore, a laser beam 3Y is output to the surface of the charged photoreceptor 1Y via the exposure device 3 in accordance with yellow image data sent from a control unit (not shown). The laser beam 3Y is applied to the photosensitive layer on the surface of the photoreceptor 1Y, whereby an electrostatic charge image of a yellow print pattern is formed on the surface of the photoreceptor 1Y.

  The electrostatic charge image is an image formed on the surface of the photoreceptor 1Y by charging, and the specific resistance of the irradiated portion of the photosensitive layer is lowered by the laser beam 3Y, and the charged charge on the surface of the photoreceptor 1Y flows. On the other hand, this is a so-called negative latent image formed by the charge remaining in the portion not irradiated with the laser beam 3Y. The electrostatic charge image formed on the photoreceptor 1Y in this way is rotated to a predetermined development position as the photoreceptor 1Y travels. At this development position, the electrostatic charge image on the photoreceptor 1Y is visualized (developed) by the developing device 4Y.

  In the developing device 4Y, for example, an electrostatic image developing developer containing at least yellow toner and a carrier is accommodated. The yellow toner is triboelectrically charged by being agitated inside the developing device 4Y, and has a charge of the same polarity (negative polarity) as the charged electric charge on the photoreceptor 1Y, and a developer roll (developer holder). Is held on. As the surface of the photoreceptor 1Y passes through the developing device 4Y, yellow toner adheres electrostatically to the static image portion that has been neutralized on the surface of the photoreceptor 1Y, and the electrostatic image is developed with the yellow toner. Is done.

  From the viewpoint of development efficiency, image graininess, gradation reproducibility, and the like, a bias potential (development bias) in which an AC component is superimposed on a DC component may be applied to the developer holder. Specifically, when the developer holding member DC applied voltage Vdc is set to, for example, −700 V or more and −300 V or less, the developer holding member AC voltage peak width Vp−p is set to a range of, for example, 0.5 kV or more and 2.0 kV or less. Good. The photoconductor 1Y on which the yellow toner image is formed continues to run at a predetermined speed, and the toner image developed on the photoconductor 1Y is conveyed to a predetermined primary transfer position.

  When the yellow toner image on the photoreceptor 1Y is conveyed to the primary transfer position, a primary transfer bias is applied to the primary transfer roller 5Y, and electrostatic force directed from the photoreceptor 1Y to the primary transfer roller 5Y is applied to the toner image. The toner image on the photoreceptor 1 </ b> Y is transferred to the intermediate transfer belt 20. The transfer bias applied at this time is a (+) polarity opposite to the polarity (−) of the toner, and is controlled to about +10 μA by the control unit (not shown) in the first unit 10Y, for example. On the other hand, the toner remaining on the photoreceptor 1Y is removed and collected by the cleaning device 6Y.

  Further, the primary transfer bias applied to the primary transfer rollers 5M, 5C, and 5K after the second unit 10M is also controlled according to the first unit. Thus, the intermediate transfer belt 20 onto which the yellow toner image has been transferred by the first unit 10Y is sequentially conveyed through the second to fourth units 10M, 10C, and 10K, and the toner images of the respective colors are superimposed and transferred in a multiple manner. The

  The intermediate transfer belt 20 onto which the four color toner images have been transferred in multiple passes through the first to fourth units is disposed on the image transfer surface side of the intermediate transfer belt 20, the support roller 24 that is in contact with the inner surface of the intermediate transfer belt 20. The secondary transfer roller (secondary transfer means) 26 is connected to a secondary transfer portion. On the other hand, a recording paper (recording medium) P is fed at a predetermined timing into a gap where the secondary transfer roller 26 and the intermediate transfer belt 20 are pressed against each other via a supply mechanism, and the secondary transfer bias is supplied to the support roller. 24. The transfer bias applied at this time is a (−) polarity that is the same polarity as the polarity (−) of the toner, and an electrostatic force from the intermediate transfer belt 20 toward the recording paper P acts on the toner image, and the transfer bias is applied to the intermediate transfer belt 20. The toner image is transferred onto the recording paper P. The secondary transfer bias at this time is determined according to the resistance detected by a resistance detection means (not shown) for detecting the resistance of the secondary transfer portion, and is voltage-controlled.

  Thereafter, the recording paper P is fed to the pressure contact portion (nip portion) of the pair of fixing rolls in the fixing device (roll-type fixing means) 28, the toner image is heated, and the color-superposed toner image is melted to record the recording paper. Fixed onto P.

  Examples of the recording medium to which the toner image is transferred include plain paper and OHP sheet used in an electrophotographic copying machine or printer.

  The recording paper P on which the color image has been fixed is carried out toward the discharge unit, and a series of color image forming operations is completed.

  The image forming apparatus exemplified above is configured to transfer the toner image onto the recording paper P via the intermediate transfer belt 20, but the present invention is not limited to this configuration, and the toner image is directly transferred from the photoconductor. It may be a structure that is transferred to a recording sheet.

  FIG. 3 is a schematic configuration diagram illustrating an example of a process cartridge containing the developer for developing an electrostatic charge image according to the present embodiment. The process cartridge 200 includes, together with the developing device 111, a photosensitive member 107, a charging roller 108, a photosensitive member cleaning device 113, an opening 118 for exposure, and an opening 117 for static elimination exposure using an attachment rail 116. Combined and integrated. In FIG. 2, reference numeral 300 indicates a recording medium.

  The process cartridge 200 is detachable from an image forming apparatus main body including a transfer device 112, a fixing device 115, and other components (not shown). It forms a forming apparatus.

  The process cartridge 200 shown in FIG. 3 includes a photoconductor 107, a charging roller 108, a developing device 111, a photoconductor cleaning device 113, an opening 118 for exposure, and an opening 117 for static elimination exposure. These devices may be selectively combined. In the process cartridge according to the present embodiment, in addition to the developing device 111, the photoconductor 107, the charging roller 108, the photoconductor cleaning device (cleaning means) 113, the opening 118 for exposure, and the discharge exposure. You may provide at least 1 sort (s) selected from the group comprised from the opening part 117. FIG.

  Next, the toner cartridge and the developer cartridge will be described. The toner cartridge is detachably attached to the image forming apparatus, and contains at least toner to be supplied to a developing unit provided in the image forming apparatus. The toner cartridge only needs to contain at least toner, and may contain developer, for example, depending on the mechanism of the image forming apparatus. A toner cartridge containing the developer is referred to as a developer cartridge.

  The image forming apparatus shown in FIG. 2 is an image forming apparatus having a configuration in which the toner cartridges 8Y, 8M, 8C, and 8K can be attached and detached, and the developing devices 4Y, 4M, 4C, and 4K are each developing devices ( And a toner supply pipe (not shown). Further, when the toner stored in the toner cartridge becomes low, the toner cartridge is replaced.

  Hereinafter, although an example and a comparative example are given and the present invention is explained more concretely in detail, the present invention is not limited to the following examples.

  As a method for measuring the molecular weight of the resin for forming the coating layer, a coating in which 5 g of carrier and 50 g of chloroform are placed in a beaker and the coating resin is sufficiently dissolved with an ultrasonic dispersing machine, and insoluble components such as magnetic core particles and conductive powder are separated by filtration. The resin extract was dried to obtain a coating resin. 20 mg of the recovered coating resin was dissolved in 10 ml of chloroform, filtered, and then measured with two GSK systems (manufactured by Tosoh Corporation) using two TSK-GEL Multipore HXL-M columns. The molecular weight was calculated from the measured chromatogram, and the number average molecular weight Mn was taken as the molecular weight.

  Volume average particle diameters of magnetic core particles, carriers, external additive particles, and the like were measured using a laser diffraction / scattering particle size distribution analyzer (product name: LS 13 320, manufactured by Beckman Coulter, Inc.).

[Preparation of coating layer-forming resin particles 1]
Cyclohexyl methacrylate monomer 97 parts by weight Acrylic acid monomer 3 parts by weight Dodecanethiol 1 part by weight is dissolved into 0.5 part by weight of an anionic surfactant (Neogen SC: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) It poured into the flask in which the aqueous solution formed by melt | dissolving in 400 mass parts of exchange water was put. Next, emulsion polymerization is carried out by introducing an aqueous solution obtained by dissolving 0.5 parts by mass of a radical polymerization initiator (ammonium persulfate) in 50 parts by mass of ion-exchanged water into the flask over 10 minutes while mixing slowly. Started. After carrying out nitrogen substitution, while stirring the inside of the flask, it was heated in an oil bath until the contents reached 70 ° C., and the temperature was maintained for 5 hours to continue emulsion polymerization. As a result, a resin particle dispersion 1 in which resin particles having a volume average particle diameter of 300 nm were dispersed was obtained. This resin particle dispersion 1 was freeze-dried to obtain resin particles 1 for forming a coating layer. The weight average molecular weight of the coating layer forming resin particles 1 was 100,000.

[Preparation of coating layer-forming resin particles 2]
Cyclohexyl methacrylate monomer 90 parts by weight Acrylic acid monomer 10 parts by weight Dodecanethiol 1 part by weight is dissolved into 0.5 part by weight of an anionic surfactant (Neogen SC: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) It poured into the flask in which the aqueous solution formed by melt | dissolving in 400 mass parts of exchange water was put. Next, emulsion polymerization is carried out by introducing an aqueous solution obtained by dissolving 0.5 parts by mass of a radical polymerization initiator (ammonium persulfate) in 50 parts by mass of ion-exchanged water into the flask over 10 minutes while mixing slowly. Started. After carrying out nitrogen substitution, while stirring the inside of the flask, it was heated in an oil bath until the contents reached 70 ° C., and the temperature was maintained for 5 hours to continue emulsion polymerization. As a result, a resin particle dispersion 2 in which resin particles having a volume average particle diameter of 250 nm were dispersed was obtained. This resin particle dispersion 2 was freeze-dried to obtain resin particles 2 for forming a coating layer. The weight average molecular weight of the coating layer forming resin particles 2 was 85,000.

[Preparation of coating layer forming resin particles 3]
A resin particle dispersion 3 in which resin particles having a volume average particle diameter of 250 nm were dispersed was produced in the same manner as the production method of the resin particles 2 for coating layer formation except that the acrylic acid monomer was changed to a maleic acid monomer. . The obtained resin particle dispersion 3 was freeze-dried to obtain resin particles 3 for forming a coating layer. The weight average molecular weight of the coating layer forming resin particles 3 was 82,000.

[Preparation of coating layer-forming resin particles 4]
A resin particle dispersion 4 in which resin particles having a volume average particle diameter of 300 nm were dispersed was produced in the same manner as the production method of the resin particles 1 for coating layer formation except that the acrylic acid monomer was changed to a methyl methacrylate monomer. . The obtained resin particle dispersion 4 was freeze-dried to obtain resin particles 4 for forming a coating layer. The weight average molecular weight of the coating layer forming resin particles 4 was 110,000.

[Preparation of coating layer-forming resin particles 5]
Resin particles having a volume average particle diameter of 310 nm were dispersed in the same manner as the method for producing the coating layer forming resin particles 1 except that 100 parts by mass of the cyclohexyl methacrylate monomer was used and no acrylic acid monomer was used. Resin particle dispersion 5 was prepared. The obtained resin particle dispersion 5 was freeze-dried to obtain resin particles 5 for forming a coating layer. The weight average molecular weight of the coating layer forming resin particles 5 was 110,000.

[Production of Resin Particle 6 for Forming Coating Layer]
A resin particle dispersion 6 in which resin particles having a volume average particle diameter of 250 nm are dispersed is produced in the same manner as the production method of the resin particles 1 for coating layer formation except that the cyclohexyl methacrylate monomer is changed to a methyl methacrylate monomer. did. The obtained resin particle dispersion 6 was freeze-dried to obtain resin particles 6 for forming a coating layer. The weight average molecular weight of the coating layer forming resin particles 6 was 120,000.

[Preparation of coating layer forming resin particle 7]
Resin particle dispersion 7 in which resin particles having a volume average particle diameter of 350 nm were dispersed was produced in the same manner as the production method of resin particles 1 for coating layer formation except that the cyclohexyl methacrylate monomer was changed to a styrene monomer. The obtained resin particle dispersion 7 was freeze-dried to obtain resin particles 7 for forming a coating layer. The weight average molecular weight of the coating layer forming resin particles 7 was 130,000.

<Example 1>
[Preparation of carrier]
Ferrite particles (Mn—Mg ferrite, true specific gravity 4.7 g / cm ³ , volume average particle size 40 μm, saturation magnetization 60 emu / g, surface roughness 1.5 μm) 100 parts by mass Resin particles 1 for coating layer formation 4.5 mass Part Carbon black 0.5 part by mass The above material is put in a 5 L Henschel mixer (manufactured by Nihon Coke Kogyo Co., Ltd.) and mixed at 2000 rpm for 60 minutes to fix the coating layer forming resin particles 1 to the ferrite particles as magnetic core particles. Made it. Further, 0.5 parts by mass of resin particles 2 for coating layer formation and 0.1 parts by mass of calcium oxide particles (volume average particle size 0.2 μm) were added, and the mixture was stirred with a Henschel mixer at 2000 rpm for 20 minutes. The mixture was stirred for 30 minutes while maintaining the temperature at 180 ° C. Thereafter, the mixture was cooled to 50 ° C. with stirring to obtain particles on which a resin coating layer was formed, and then the obtained resin coating layer-forming particles were sieved with a mesh having an opening of 75 μm to obtain Carrier 1.

  The obtained carrier 1, zirconia beads, and water were mixed in a glass container, stirred with a ball mill while confirming the layer thickness of the resin coating layer, and zirconia when the layer thickness of the resin coating layer was polished by 10% or more. The carrier 1 after the abrasion treatment was obtained by removing the beads and water and drying. The layer thickness of the resin coating layer was measured in advance by cutting the carrier with a microtome and analyzing the cross section. 5 g of carrier 1 and carrier 1 subjected to abrasion treatment of carrier 1 and 50 g of chloroform were each placed in a beaker, and the coating resin was sufficiently dissolved with an ultrasonic disperser. Next, the coated resin extract from which insoluble components such as magnetic core particles and conductive powder are separated by filtration is dried, 20 mg of the collected coated resin is dissolved in 10 ml of chloroform, filtered, and the solution is analyzed by infrared absorption spectrum. By analyzing by the method, the presence or absence of metal crosslinking in the coating resin in each carrier was analyzed. As a result, metal crosslinking was confirmed in the coating resin of the carrier 1 before the abrasion treatment, and no metal crosslinking was confirmed in the coating resin contained in the carrier 1 after the abrasion treatment (below the detection limit).

[Preparation of Toner 1 and Developer 1]
HMDS treatment with 100 parts by mass of toner particles (manufactured by Fuji Xerox Co., Ltd., 5.8 μm toner) and 1.2 parts by mass of silicone oil-treated silica particles having a volume average particle size of 40 nm (RY50: manufactured by Nippon Aerosil Co., Ltd.) Toner 1 containing external additive particles was obtained by mixing 1.5 parts by mass of silica particles with a sample mill.

  8 parts by mass of the toner 1 and 100 parts by mass of the carrier 1 were stirred at 40 rpm for 20 minutes using a V blender, and then subjected to sieving using a 125 μm mesh sieve to obtain developer 1.

[Evaluation of carrier and developer]
The developer 1 was used and left for 12 hours in a 5 ° C., 20% RH environment using a modified copy machine Docu Center Color 500 manufactured by Fuji Xerox Co., Ltd. 1,000 sheets were printed. Print chart after initial (10th sheet), 1000th sheet, 10,000 sheet, 50,000 sheet and 100,000 sheet print, and printed chart after standing for 72 hours after printing 100,000 sheet Evaluation of printing density stability and evaluation of image defects using image smudge and fine line reproducibility as evaluation items were performed according to the following criteria. The obtained results are shown in Tables 1 and 2.

(Print density stability)
The print density difference (density difference) between the 10th print chart and the 1000th, 10,000th, 50,000th, and 100,000th print charts is expressed as X-Rite 939 (X-Rite). The measurement was performed using It is preferable that the difference in the print density is small. If the absolute value of the print density difference is within 0.03, it is evaluated that the print density is stable.

(Image dirt)
In the print chart, image quality stains appearing as non-image area stains or image disturbances were visually observed and evaluated according to the following criteria.
○: When image stains cannot be confirmed visually △: When image stains can be confirmed visually but unclear ×: Image stains can be clearly confirmed visually

(Fine line reproducibility)
Using the developer 1 and the modified machine, the sheet was allowed to stand for 12 hours in an environment of 20 ° RH at 5 ° C., and 100,000 sheets of 1% printing charts were printed on A4 paper in the same environment. 2,400 dpi for the initial (10th sheet), 1,000th sheet, 10,000 sheet, 50,000 sheet, and 100,000 sheet, and after leaving for 100,000 hours after printing 100,000 sheets A 1 on 1 off image (an image in which one dot line is arranged in parallel at an interval of one dot) was output to the upper left, center, and lower right of the A4 paper as a 5 cm × 5 cm chart perpendicular to the developing direction. About the line interval of each chart printed on the output sample, using a magnifying glass with a scale of × 100 times, it is narrowed due to toner scattering, etc., or it is widened by narrowing the thin line We observed whether there was any. Grade evaluation was performed based on the following criteria from the observation results and the line spacing of the observed locations. The obtained results are shown in Table 1.
○: All charts show almost no decrease in line spacing due to scattering, or little increase in line spacing due to thinning of thin lines. Δ: At least one chart in which thin lines can be confirmed although there is a decrease or increase in line spacing. When there is x: When the interval between the thin lines cannot be determined or there is at least one chart in which the thin lines are missing

<Example 2>
A carrier 2 and a developer 2 were produced in the same manner as in Example 1 except that the coating layer forming resin particles 2 in Example 1 were changed to coating layer forming resin particles 3, and under the same conditions as in Example 1. The print density stability, image smear, and fine line reproducibility were evaluated. The obtained results are shown in Tables 1 and 2.

<Example 3>
A carrier 3 and a developer 3 were produced in the same manner as in Example 1 except that the calcium oxide particles in Example 1 were changed to zinc oxide particles (volume average particle size 0.15 μm). The same conditions as in Example 1 were obtained. Were evaluated for print density stability, image smearing, and fine line reproducibility. The obtained results are shown in Tables 1 and 2.

<Example 4>
A carrier 2 and a developer 2 were produced in the same manner as in Example 1 except that the coating layer forming resin particles 1 in Example 1 were changed to coating layer forming resin particles 4, and under the same conditions as in Example 1. The print density stability, image smear, and fine line reproducibility were evaluated. The obtained results are shown in Tables 1 and 2.

<Example 5>
A carrier 5 and a developer 5 were produced in the same manner as in Example 1 except that the coating layer forming resin particles 2 in Example 1 were changed to coating layer forming resin particles 1, and under the same conditions as in Example 1. The print density stability, image smear, and fine line reproducibility were evaluated. The obtained results are shown in Tables 1 and 2.

<Example 6>
A carrier 6 and a developer 6 were prepared in the same manner as in Example 1 except that the coating layer forming resin particles 1 and 2 in Example 1 were changed to coating layer forming resin particles 6, respectively. Under the same conditions, print density stability, image smear, and fine line reproducibility were evaluated. The obtained results are shown in Tables 1 and 2.

<Example 7>
A carrier 7 and a developer 7 were prepared in the same manner as in Example 1 except that the coating layer forming resin particles 1 and 2 in Example 1 were changed to coating layer forming resin particles 7, respectively. Under the same conditions, print density stability, image smear, and fine line reproducibility were evaluated. The obtained results are shown in Tables 1 and 2.

<Example 8>
100 parts by weight of toner particles (manufactured by Fuji Xerox Co., Ltd., 5.8 μm toner) and 1.2 parts by weight of silicone oil-treated silica particles (RY50: manufactured by Nippon Aerosil Co., Ltd.) having an average particle size of 40 nm, HMDS-treated silica having an average particle size of 50 nm Toner 2 containing external additive particles was obtained by mixing 1.5 parts by mass of the particles with a sample mill.
A developer 8 is produced in the same manner as in Example 1 except that the toner 1 in Example 1 is changed to the toner 2, and the print density stability, image smear, and fine line reproducibility are the same as in Example 1. Evaluation was performed. The obtained results are shown in Tables 1 and 2.

<Example 9>
HMDS-treated silica having 100 parts by mass of toner particles (manufactured by Fuji Xerox Co., Ltd., 5.8 μm toner) and 1.5 parts by mass of silicone oil-treated silica particles having an average particle size of 40 nm (RY50: manufactured by Nippon Aerosil Co., Ltd.). Toner 3 containing external additive particles was obtained by mixing 1.5 parts by mass of the particles with a sample mill.
A developer 9 is produced in the same manner as in Example 1 except that the toner 1 in Example 1 is changed to the toner 3, and print density stability, image smear, and fine line reproducibility are the same as in Example 1. Evaluation was performed. The obtained results are shown in Tables 1 and 2.

<Comparative Example 1>
A carrier 10 and a developer 10 were prepared in the same manner as in Example 1 except that heating at 180 ° C. for 30 minutes was not performed. Under the same conditions as in Example 1, printing density stability, image smearing, and fine line reproducibility were obtained. Evaluation was performed. The obtained results are shown in Tables 1 and 2.

<Comparative Example 2>
A carrier 11 and a developer 11 were prepared in the same manner as in Example 1 except that the coating layer forming resin particles 1 and 2 in Example 1 were changed to coating layer forming resin particles 4, and the same conditions as in Example 1 were obtained. Were evaluated for print density stability, image smearing, and fine line reproducibility. The obtained results are shown in Tables 1 and 2.

<Comparative Example 3>
A carrier 12 and a developer 12 were prepared in the same manner as in Example 1 except that the coating layer forming resin particles 1 and 2 in Example 1 were changed to coating layer forming resin particles 5, and the same conditions as in Example 1 were obtained. Were evaluated for print density stability, image smearing, and fine line reproducibility. The obtained results are shown in Table 1 and Table.

<Comparative Example 4>
A carrier 13 and a developer 13 were prepared in the same manner as in Example 1 except that the calcium oxide particles of Example 1 were not used. Under the same conditions as in Example 1, printing density stability, image smearing, and fine line reproducibility were obtained. Evaluation was performed. The obtained results are shown in Tables 1 and 2.

<Comparative Example 5>
Ferrite particles (Mn—Mg ferrite, true specific gravity 4.7 g / cm ³ , volume average particle size 40 μm, saturation magnetization 60 emu / g, surface roughness 1.5 μm) 100 parts by mass Resin particles 1 for coating layer formation 5.0 mass Parts Carbon black 0.5 parts by mass Calcium oxide particles (volume average particle size 0.2 μm) 1.0 parts by mass The above materials were put into a 5 L Henschel mixer (manufactured by Nippon Coke Industries Co., Ltd.), mixed at 2000 rpm for 60 minutes, and coated The layer forming resin particles 1 were fixed to the ferrite particles. Furthermore, after stirring for 20 minutes at 2000 rpm with a Henschel mixer, it stirred for 30 minutes, maintaining the temperature in a mixer at 180 degreeC. Then, it cooled to 50 degreeC, stirring, and obtained the particle | grains in which the resin coating layer was formed, Then, the obtained resin coating layer formation particle | grain was sieved with the net | network of 75 micrometers of openings, and the carrier 14 was obtained. Developer 1 was prepared in the same manner as in Example 1, and print density stability, image smear, and fine line reproducibility were evaluated under the same conditions as in Example 1. The obtained results are shown in Tables 1 and 2.

<Comparative Example 6>
Ferrite particles (Mn—Mg ferrite, true specific gravity 4.7 g / cm ³ , volume average particle size 40 μm, saturation magnetization 60 emu / g, surface roughness 1.5 μm) 100 parts by mass Resin particles 1 for coating layer formation 2.5 mass Part Carbon black 0.3 part by mass The above material is put into a 5 L Henschel mixer (manufactured by Nihon Coke Kogyo Co., Ltd.) and mixed at 2000 rpm for 60 minutes to fix the coating layer forming resin particles 1 to the ferrite particles as magnetic core particles. Made it. Further, 2.0 parts by mass of resin particles 2 for forming the coating layer, 0.2 parts by mass of carbon black, and 0.1 parts by mass of calcium oxide particles (volume average particle size 0.2 μm) were added, and 20 at 2000 rpm with a Henschel mixer. After stirring for 5 minutes, 0.5 parts by weight of resin particles 2 for forming the coating layer and 0.1 parts by weight of calcium oxide particles (volume average particle size 0.2 μm) were added, and after stirring for 20 minutes at 2000 rpm with a Henschel mixer. The mixture was stirred for 30 minutes while maintaining the temperature in the mixer at 180 ° C. Thereafter, the mixture was cooled to 50 ° C. with stirring to obtain particles on which a resin coating layer was formed, and then the obtained resin coating layer-forming particles were sieved with a mesh having an opening of 75 μm to obtain a carrier 15. Developer 15 was prepared in the same manner as in Example 1, and print density stability, image smearing, and fine line reproducibility were evaluated under the same conditions as in Example 1. The obtained results are shown in Tables 1 and 2.

  As the results of Examples 1 to 9 show, the magnetic core material particles having a resin coating layer are contained, the resin coating layer contains a resin containing a monomer unit having a carboxy group, and the resin coating layer has a surface layer, By using a carrier having a crosslinked structure of a carboxy group contained in the resin and a metal having a valence of 2 or more, a change in printing density at the beginning of use of the developer as compared with Comparative Examples 1 to 6 Even after long-term image formation under low temperature and low humidity, image defects were suppressed, such as image smearing being suppressed and fine line reproducibility being improved while securing a stable printing density.

  1Y, 1M, 1C, 1K, 107, 314 photoconductor (electrophotographic photoconductor), 2Y, 2M, 2C, 2K, 108, 310 charging roller (charging unit), 3,110, 312 exposure device (exposure unit), 3Y, 3M, 3C, 3K laser beam, 4Y, 4M, 4C, 4K, 111, 316 developing device (developing unit), 5Y, 5M, 5C, 5K, 112, 318 primary transfer roller (transfer unit), 6Y, 6M, 6C, 6K, 113, 320 Photoconductor cleaning device (cleaning unit), 8Y, 8M, 8C, 8K toner cartridge, 10Y, 10M, 10C, 10K image forming (unit), 20 intermediate transfer belt, 22 driving roller, 24 support roller, 26 secondary transfer roller, 28, 115, 322 fixing device (fixing unit), 30 intermediate transfer member cleaning 112, transfer device, 116 mounting rail, 117 opening for static elimination exposure, 118 opening for exposure, 200 process cartridge, 300, 324, P recording paper (recording medium), 301 image forming apparatus.

Claims (8)

  Containing at least a magnetic core particle and a resin coating layer covering a surface of the magnetic core particle, the resin coating layer containing a resin containing a monomer unit having a carboxy group, A carrier for developing an electrostatic charge image, wherein the surface layer has a crosslinked structure of a carboxy group contained in the resin and a metal having a valence of 2 or more.   The electrostatic charge image according to claim 1, wherein the resin containing a monomer unit having a carboxy group includes a copolymer resin of a (meth) acrylic acid ester monomer and a monomer containing a carboxy group and an ethylenically unsaturated group. Development carrier.   The electrostatic charge image developing carrier according to claim 2, wherein the (meth) acrylic acid ester monomer is an alicyclic methacrylic acid ester monomer.   An electrostatic charge image developing developer comprising the electrostatic charge image developing carrier according to claim 1 and an electrostatic charge image developing toner.   An electrostatic charge comprising: the electrostatic charge image developing carrier according to claim 1; and an electrostatic charge image developing toner having external additive particles having a volume average particle diameter of 50 nm to 200 nm. Developer for image development.   A developer cartridge containing the developer for developing an electrostatic image according to claim 4.   A developing means for storing a developer for developing an electrostatic charge image according to claim 4 or 5, and developing a toner image by developing the electrostatic charge image formed on the surface of the image carrier with the developer for developing an electrostatic charge image. And a process cartridge that is detachably attached to the image forming apparatus. 6. The image carrier, charging means for charging the surface of the image carrier, electrostatic charge image forming means for forming an electrostatic image on the surface of the image carrier, and the electrostatic image according to claim 5. An image forming apparatus comprising: a developing unit that forms a toner image by developing with an electrostatic charge image developing developer; and a transfer unit that transfers the toner image to a recording medium.

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