JP2011090168A - Toner for developing electrostatic charge image, developer for developing electrostatic charge image and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a toner for developing an electrostatic charge image, in which the fixation of a resin fine particle, that suppresses the poor electrification of the toner excellently, to a toner base particle is promoted to ensure image quality over a long period of time. <P>SOLUTION: The toner for developing the electrostatic charge image is prepared by adding an external additive to the toner base particle. The external additive includes the resin fine particles having the electrostatic property of the polarity reverse to that of the toner base particle. An inorganic fine particle having the particle size smaller than that of the resin fine particle is mixed in the resin fine particle. The resin fine particle is an acrylic copolymer, an acrylic homopolymer, a methacrylic copolymer and/or a methacrylic homopolymer and the inorganic fine particle is silica, alumina and/or titania. The particle size of the resin fine particle is 70-300 nm and that of the inorganic fine particle is 15-50 nm. The amount of the inorganic fine particle to be mixed in 100 parts mass resin fine particle is 50-150 parts mass. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electrostatic image developing toner, an electrostatic image developing developer, and an image forming apparatus used in an electrophotographic system.

  In an image forming apparatus such as a copying machine, a printer, or a digital multifunction machine that forms an image on a sheet by electrophotography, an electrostatic charge image (electrostatic latent image) formed on the peripheral surface of a photosensitive drum as an image carrier However, the toner is developed with toner by a developing device, and is visualized as a toner image. The toner image on the photosensitive drum is transferred onto a sheet by a transfer device, and then heated and pressed by a fixing device to be fixed on the sheet. The sheet on which the toner image is fixed is finally discharged out of the image forming apparatus.

  In general, an electrostatic image developing toner used in such an electrophotographic system is obtained by adding an external additive to a toner raw powder (also referred to as toner base particles or bulk toner) in which a colorant or the like is blended with a binder resin. It is a configuration. External additives improve toner fluidity, improve toner charging stability, stabilize the adhesion of toner to a toner carrier such as a developing sleeve or a photosensitive drum, and suppress direct contact between toner powders. Therefore, it is added to the toner raw powder. Examples of such external additives include inorganic fine particles such as silica, alumina, and titania, for example, acrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, and methacrylic acid. Acrylic polymer which is a homopolymer or copolymer (copolymer) of acrylic monomers such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, propyl methacrylate Or, for example, a styrene polymer that is a homopolymer or copolymer of a styrene monomer such as styrene, methyl styrene, ethyl styrene, dimethyl styrene, n-butyl styrene, chlorostyrene, or the above acrylic monomer Styrene-acrylic acid, which is a copolymer of the styrene monomer and Resin fine particles such as Le polymer is used (see Patent Document 1).

  The resin fine particles have a frictional charge series similar to the binder resin of the toner raw powder compared to the inorganic fine particles. Therefore, even if the resin fine particles are embedded in the toner raw powder due to thermal stress or mechanical stress, the charging ability of the toner is reduced. It has the characteristics of being suppressed and excellent in suppressing toner charging defects.

JP 2002-296829 A (paragraphs 0083, 0084, 0086)

However, since the resin fine particles have a specific gravity as low as about 1 to 1.2 g / cm ^3, there is a problem that the resin fine particles are easily detached from the surface of the toner raw powder and difficult to be fixed on the surface of the toner raw powder. As a result, not only does the resin fine particle characteristic of excellent suppression of toner charging failure not be fully exhibited, but also the resin fine particles detached from the surface of the toner raw powder contaminate the toner carrier such as the developing sleeve and the photosensitive drum. In addition, the heat in the image forming apparatus may be melted and fixed to the toner carrier to cause fogging or image defects.

  An object of the present invention is to promote the fixation of resin fine particles excellent in suppression of toner charging failure to a toner raw powder, thereby ensuring image quality over a long period of time.

  That is, one aspect of the present invention is an electrostatic charge image developing toner in which an external additive is added to a toner raw powder, and the external additive includes resin fine particles having a chargeability opposite to that of the toner raw powder. This is an electrostatic charge image developing toner in which inorganic fine particles having a particle diameter smaller than that of the resin fine particles are combined with the resin fine particles.

  According to this configuration, since the resin fine particles have a chargeability opposite to that of the toner raw powder, the fixing of the resin fine particles to the toner raw powder is electrostatically promoted, and the resin fine particles are not easily detached from the toner raw powder. Become. In addition, since the inorganic fine particles are combined with the resin fine particles, the specific gravity of the resin fine particles is increased, which also promotes the fixing of the resin fine particles to the toner raw powder, and the resin fine particles are not easily detached from the toner raw powder. Become. In addition, since the particle diameter of the inorganic fine particles is smaller than the particle diameter of the resin fine particles, the main component of the composite particles is the resin fine particles. Synergistically, the characteristics of the resin fine particles that are excellent in suppressing toner charging failure are exhibited well, and the resin fine particles detached from the surface of the toner raw powder contaminate the toner carrier or carry the toner. The problem that the film is melted and fixed to the body to cause fogging and image defects is satisfactorily suppressed.

  In the above configuration, the resin fine particles are at least one selected from the group consisting of an acrylic copolymer, an acrylic homopolymer, a methacrylic copolymer, and a methacrylic homopolymer. For example, the charging stability of the toner is further improved. From the viewpoint of the above.

  In the above configuration, the inorganic fine particles are at least one selected from the group consisting of silica, alumina and titania, which are used alone as an external additive, for example, the specific gravity of the resin fine particles is surely increased. This is preferable from the viewpoint of further improving the fluidity of the toner.

  In the above configuration, the resin fine particles have a particle diameter of 70 to 300 nm and the inorganic fine particles have a particle diameter of 15 to 50 nm. For example, the resin fine particles are excessively liable to be detached from the toner raw powder. It is preferable from the viewpoint of avoidance and easy availability of raw materials.

  Further, in the above configuration, the amount of the inorganic fine particles based on 100 parts by mass of the resin fine particles is 50 to 150 parts by mass, for example, the characteristics of the resin fine particles (excellent in improving the charging stability of the toner) and the inorganic fine particles From the viewpoint of achieving a good balance between the above properties (excellent improvement in toner fluidity, etc.).

  Further, the electrostatic charge image developing toner is used in an image forming apparatus having a developing sleeve whose surface is coated with a resin. For example, resin fine particles detached from the surface of the toner raw powder are on the surface of the developing sleeve. It is preferable from the viewpoint of effectively eliminating the concern of being melted and fixed.

  Another aspect of the present invention is a developer for developing an electrostatic image comprising the toner for developing an electrostatic image and a carrier. According to this configuration, a two-component developer having the various functions described above can be obtained.

  Still another aspect of the present invention is an image forming apparatus using the electrostatic image developing toner or the electrostatic image developing developer. According to this configuration, an image forming apparatus having the various functions described above can be obtained.

  According to the present invention, since the fixing of the resin fine particles excellent in suppression of charging failure of the toner to the toner raw powder is promoted, the resin fine particles detached from the surface of the toner raw powder are removed from the toner such as the developing sleeve and the photosensitive drum. Problems such as contamination of the carrier or melting and fixing to the toner carrier by heat in the image forming apparatus, leading to fogging and image defects, can be prevented, and long-term image quality can be ensured.

[Toner for electrostatic image development]
The toner for developing an electrostatic charge image according to the present invention has a configuration in which an external additive is added to a toner raw powder. The external additive contains resin fine particles having the chargeability opposite to that of the toner raw powder. Further, inorganic fine particles having a particle diameter smaller than that of the resin fine particles are combined with the resin fine particles.

<Toner powder>
The toner raw powder is obtained by blending a binder resin with a colorant, a release agent, a charge control agent, or the like. The toner raw powder is produced, for example, by mixing these raw materials with a mixer or the like, melting and kneading with an extruder or the like, cooling, pulverizing and classifying the obtained solid. The volume average particle diameter of the toner raw powder is 2 to 12 μm, more preferably 4 to 10 μm, and still more preferably 6 to 8 μm. In the present invention, the toner raw powder is preferably a true sphere having a high degree of circularity (close to 1), but may be, for example, a cylindrical shape depending on the situation.

(Binder resin)
In the present invention, as the binder resin, those conventionally used as a binder resin for toner raw powder can be used without any particular limitation. Specific examples thereof include, for example, styrene resins, acrylic resins, styrene-acrylic resins, polyethylene resins, polypropylene resins, vinyl chloride resins, polyester resins, polyamide resins, polyurethane resins, polyvinyl alcohol resins. Examples thereof include thermoplastic resins such as resins, vinyl ether resins, N-vinyl resins, and styrene-butadiene resins. These may be used alone or in combination of two or more.

  In the present invention, as the binder resin, it is preferable to use the thermoplastic resin as described above from the viewpoint of good fixability, but it is not necessary to use only the thermoplastic resin. A part of the functional resin may be used. Thus, by introducing a partially crosslinked structure into the binder resin, it is possible to improve the storage stability, form retention or durability of the toner without deteriorating the fixability.

  Examples of the thermosetting resin that can be used in the present invention include bisphenol A type epoxy resins, hydrogenated bisphenol A type epoxy resins, novolac type epoxy resins, polyalkylene ether type epoxy resins, cyclic aliphatic type epoxy resins, and cyanates. Examples thereof include resins. These may be used alone or in combination of two or more.

  For example, the glass transition temperature of the binder resin is preferably 50 to 70 ° C, and more preferably 55 to 65 ° C. When the glass transition temperature of the binder resin is less than 50 ° C., the toners are fused in the developing device during operation of the image forming apparatus, or the toners are fused in the container during storage or transportation of the toner. In addition, the storage stability of the toner tends to decrease. On the other hand, when the glass transition temperature of the binder resin exceeds 70 ° C., the low-temperature fixability of the toner tends to decrease.

  The chargeability of the binder resin constituting the toner raw powder is determined by the molecular structure of the polymer constituting the resin. In general, a polymer having an amino group exhibits a positive chargeability, and a polymer having a carboxylic acid or a fluorine atom exhibits a negative chargeability, but is not limited thereto. For example, positively chargeable resin particles are obtained by (1) a method of reacting a nitrogen-containing compound on the surface of the resin particles, (2) a method of synthesis using an amino monomer (such as dimethylaminoethyl acrylate), and (3) a nitrogen-containing polymerization. It can be produced by a method of synthesis using an initiator (amidinopropane hydrochloride or the like). On the other hand, negatively chargeable resin particles include (1) a method of reacting a zinc complex on the surface of the resin particles, (2) a method of synthesis using a methacrylic acid monomer, and (3) a fluorine-containing monomer (such as trifluoroethyl methacrylate). It can be produced by a method of synthesis using

(Coloring agent)
In the present invention, as the colorant, those conventionally used as a colorant for monochrome toners or color toners can be used without particular limitation. Specific examples thereof include black pigments such as carbon black, yellow pigments such as pigment yellow 180, orange pigments such as molybdenum orange, C.I. I. Examples thereof include red pigments such as Pigment Red 238, purple pigments such as methyl violet lake, blue pigments such as phthalocyanine blue, green pigments such as Pigment Green B, and various dyes.

  In this invention, the compounding quantity of a coloring agent is 1-15 mass parts with respect to 100 mass parts of binder resin, for example.

(Release agent)
In the present invention, the release agent is blended for the purpose of improving the fixing property of the toner and preventing the offset property from being lowered. In the present invention, as the release agent, those conventionally used as a release agent for toner raw powder can be used without any particular limitation. Specific examples thereof include polyethylene wax, polypropylene wax, Teflon (registered trademark) wax, Fischer-Tropsch wax, paraffin wax, ester wax, carbana wax, montan wax, rice wax, and the like. These may be used alone or in combination of two or more.

  In this invention, the compounding quantity of a mold release agent is 1-5 mass parts with respect to 100 mass parts of binder resin, for example. When the blending amount of the release agent is less than 1 part by mass, there is a tendency that improvement in toner fixing property and prevention of deterioration in offset property are not satisfactorily achieved. On the other hand, when the compounding amount of the release agent exceeds 5 parts by mass, the toners are fused, and the storage stability of the toner tends to be lowered.

(Charge control agent)
In the present invention, the charge control agent is blended for the purpose of maintaining the charge amount of the toner and improving the charge rising characteristic (characteristic of charging to a predetermined charge amount in a short time). When the toner is positively charged and used for development, a positively chargeable charge control agent is used. When the toner is negatively charged and used for development, a negatively chargeable charge control agent is used.

  In the present invention, as the positively chargeable charge control agent, those conventionally used as the positively chargeable charge control agent of the toner raw powder can be used without particular limitation. Specific examples thereof include azine compounds such as pyridazine, pyrimidine, pyrazine, orthooxazine, metaoxazine, paraoxazine, orthothiazine, metathiazine, parathiazine, and 1,2,3-triazine. These may be used alone or in combination of two or more.

  In the present invention, as the negatively chargeable charge control agent, those conventionally used as the negatively chargeable charge control agent of the toner raw powder can be used without particular limitation. Specific examples thereof include organometallic complexes such as acetylacetone metal complexes and salicylic acid metal complexes, and chelate compounds such as aluminum acetylacetonate and iron (II) acetylacetonate. These may be used alone or in combination of two or more.

  In this invention, the compounding quantity of an electric charge control agent is 0.5-15 mass parts with respect to 100 mass parts of binder resin, for example. When the blending amount of the charge control agent is less than 0.5 parts by mass, the image density tends to decrease, it becomes difficult to maintain the image density, fogging increases, and contamination of the photosensitive drum tends to increase. On the other hand, when the blending amount of the charge control agent exceeds 15 parts by mass, there is a tendency that charging failure / image failure under high temperature and high humidity increases and contamination of the photosensitive drum increases.

<External additive>
The external additive is the central feature of the present invention. First, resin fine particles are used as the external additive. In the present invention, as the resin fine particles, those conventionally used as external additives added to the toner raw powder can be used without any particular limitation. Specific examples thereof include acrylic resin fine particles mainly composed of acrylic resin, methacrylic resin fine particles mainly composed of methacrylic resin, and fluorine resin fine particles mainly composed of fluorine resin. . These may be used alone or in combination of two or more. Among these, acrylic copolymers, acrylic homopolymers (for example, styrene-acrylic resins), methacrylic copolymers and / or methacrylic homopolymers (for example, styrene-methacrylic resins) are preferable. This is because the charging stability of the toner is further improved.

  Examples of the acrylic monomer used as the raw material for the acrylic copolymer or acrylic homopolymer include acrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, and propyl acrylate. , N-octyl acrylate, dodecyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate, dimethylaminoethyl acrylate, acrylic acid And diethylaminoethyl.

  Examples of methacrylic monomers used as raw materials for methacrylic copolymers or methacrylic homopolymers include, for example, methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, propyl methacrylate. , N-octyl methacrylate, dodecyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, 2-chloroethyl methacrylate, phenyl methacrylate, α-chloromethyl methacrylate, dimethylaminoethyl methacrylate, methacrylic acid And diethylaminoethyl.

  Examples of the styrene monomer used as a raw material for the styrene-acrylic resin or styrene-methacrylic resin include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, and p-ethyl. Styrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene , Pn-dodecylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, and the like.

  In the present invention, the resin fine particles used as an external additive for the toner have a chargeability opposite to that of the toner powder. As a result, the fixing of the resin fine particles to the toner raw powder is electrostatically promoted, and the resin fine particles are hardly detached from the toner raw powder.

  For example, in a regular development method (a method in which a toner charged to a polarity opposite to the charged polarity of a photosensitive drum is used and a charged toner is attached to a portion not irradiated with light to develop an electrostatic image), When the positive electrode is charged, a negatively chargeable toner powder is used, and therefore, resin fine particles as an external additive are positively charged. On the contrary, when the photosensitive drum is initially charged to the negative electrode, the toner raw powder is positively charged, and therefore the resin fine particles as external additives are negatively charged.

  In a reversal development method (a method in which a toner charged to the same polarity as the charging polarity of a photosensitive drum is used and a charged toner is attached to a portion irradiated with light to develop an electrostatic image), When the positive electrode is initially charged, since the toner raw powder is positively charged, the resin fine particles as the external additive are negatively charged. Conversely, when the photosensitive drum is initially charged to the negative electrode, the toner raw powder is negatively charged, so that the resin fine particles as external additives are positively charged.

  The chargeability of the resin fine particles used as the external additive is determined by the molecular structure of the polymer constituting the resin. In general, a polymer having an amino group exhibits a positive chargeability, and a polymer having a carboxylic acid or a fluorine atom exhibits a negative chargeability, but is not limited thereto. For example, positively chargeable resin particles are obtained by (1) a method of reacting a nitrogen-containing compound on the surface of the resin particles, (2) a method of synthesis using an amino monomer (such as dimethylaminoethyl acrylate), and (3) a nitrogen-containing polymerization. It can be produced by a method of synthesis using an initiator (amidinopropane hydrochloride or the like). On the other hand, negatively chargeable resin particles include (1) a method of reacting a zinc complex on the surface of the resin particles, (2) a method of synthesis using a methacrylic acid monomer, and (3) a fluorine-containing monomer (such as trifluoroethyl methacrylate). It can be produced by a method of synthesis using

  In the present invention, resin fine particles used as an external additive for toner are composites of inorganic fine particles. This increases the specific gravity of the resin fine particles, promotes the fixation of the resin fine particles to the toner raw powder, and makes it difficult for the resin fine particles to be detached from the toner raw powder.

  In the present invention, the inorganic fine particles may appear on the surface of the resin fine particles, or may be embedded in the resin fine particles. Particles in which resin fine particles and inorganic fine particles are combined have characteristics of resin fine particles (excellent in improving charging stability of toner) and inorganic fine particles (excellent in improving fluidity of toner). It is a composite particle comprising both.

  Such a composite of different kinds of particles is, for example, a method in which inorganic fine particles are attached to the surface of resin fine particles, and mechanical impact force or shear force is applied in this state to fix the inorganic fine particles to resin fine particles. It is feasible. That is, a physicochemical change (mechanochemical effect) generated on the surface of the fine particles by the action of mechanical energy is utilized. Such compounding can be achieved by using, for example, an ang mill, a hybridizer, a coat mizer, a disper coat, a jet mizer or the like. More specifically, Ongmill manufactured by Hosokawa Micron, Sheeter Composer manufactured by Okada Seiko, Hybridizer manufactured by Nara Machinery Co., Ltd. It is.

  In the present invention, the particle size of the inorganic fine particles is smaller than the particle size of the resin fine particles. As a result, the main component of the combined particles is resin fine particles. In addition, the resin fine particles are excellent in suppressing the charging failure of the toner in synergy with the fact that the fixing of the resin fine particles to the toner raw powder is promoted and the resin fine particles are difficult to be detached from the toner raw powder. Demonstrated. As a result, the problem of fogging and toner scattering, which is caused by the occurrence of toner having a negatively charged property and a toner having a negative polarity, is satisfactorily suppressed.

  In the present invention, the inorganic fine particles are preferably silica, alumina and / or titania which can be used alone as an external additive. This is because the specific gravity of the resin fine particles is surely increased. In addition, the fluidity of the toner is further improved.

In general, the specific gravity of resin fine particles is as light as about 1 to 1.2 g / cm ³ , while the specific gravity of silica fine particles produced by a sol-gel method is about 1.4 to 1.9 g / cm ^{3, for} example. The specific gravity of the silica fine particles is approximately 2.2 g / cm ³ . Further, the specific gravity of the alumina particles is approximately 3.97 g / cm ^3, the specific gravity of the titania fine particles in rutile in anatase type, there approximately 4.23 g / cm ^3. Therefore, by compounding such inorganic fine particles, the specific gravity of the resin fine particles (composite particles) is surely increased. As a result, the fixing of the resin fine particles to the toner raw powder is promoted, and the resin fine particles are difficult to be detached from the toner raw powder.

  Of silica, alumina, and titania, titania is most preferable because of its large specific gravity.

  In the present invention, the particle diameter (number average primary particle diameter) of the resin fine particles is preferably 70 to 300 nm, more preferably 70 to 200 nm, and further preferably 70 to 99 nm. Resin fine particles having a particle diameter of less than 70 nm are difficult to obtain. When the particle diameter of the resin fine particles exceeds 300 nm, the resin fine particles become excessive and easily detached from the toner raw powder.

  The particle diameter (number average primary particle diameter) of the inorganic fine particles is preferably 15 to 50 nm and more preferably 15 to 35 nm or 35 to 50 nm with respect to the particle diameter of such resin fine particles. When the particle diameter of the inorganic fine particles is less than 15 nm, the characteristics of the inorganic fine particles (such as excellent improvement in toner fluidity) hardly appear. When the particle diameter of the inorganic fine particles exceeds 50 nm, the particle diameter of the resin fine particles is excessively approached, and the main component of the combined particles is not the resin fine particles.

  In the present invention, the mixing ratio of the resin fine particles and the inorganic fine particles is preferably 50 to 150 parts by mass of the inorganic fine particles with respect to 100 parts by mass of the resin fine particles, and 60 to 140 parts by mass of the inorganic fine particles with respect to 100 parts by mass of the resin fine particles. More preferably, it is 100 parts by mass. Good resin fine particle characteristics (excellent in improving charging stability of toner) and inorganic fine particles (excellent in improving fluidity of toner) in the composite particles of resin fine particles and inorganic fine particles It is because it balances with.

  In the present invention, in addition to such composite particles of resin fine particles and inorganic fine particles, those conventionally used as toner external additives can be used in combination without any particular limitation. Specific examples thereof include, for example, a dry high-temperature hydrolysis method (a dry method in which silicon chloride such as silicon tetrachloride is vaporized and a silica fine particle is synthesized by a gas phase reaction in a high-temperature hydrogen flame). Silica produced by fumed silica, deflagration method (dry method of synthesizing silica fine particles by oxidizing silicon in a stream of oxygen and cooling it to vapor with its reaction heat), sol-gel method (hydration of alkoxysilane) Silica produced by a wet method for synthesizing silica fine particles by decomposition), silica produced by a colloidal method (wet method for synthesizing silica fine particles by hydrolysis of water glass), sulfuric acid method, chlorine method or dry high-temperature water addition Examples thereof include titania, alumina, silicon carbide, metal soap, non-complexed resin fine particles synthesized by a decomposition method, and the like. These may be used alone or in combination of two or more.

  In the present invention, the surface of the external additive can be hydrophobized using a silane coupling agent such as silicone oil, aminosilane, hexamethyldisilazane, etc., or a titanate coupling agent, depending on the situation. You may process.

  In the present invention, the external additive is more preferably a true sphere having a high degree of circularity (close to 1).

  The external addition process for preparing the toner by adding the external additive to the toner raw powder is performed by stirring and mixing the toner raw powder and the external additive in a dry manner. In this case, the stirring and mixing is preferably performed using a Henschel mixer, a Nauter mixer, or the like so that the external additive as fine particles is not buried in the surface of the toner raw powder.

  In the present invention, the additive amount of the external additive that has been conventionally used can be used without any particular limitation as the additive amount of the toner powder. For example, the external additive is 0.5 to 5.0 parts by mass, and more preferably 1.5 to 3.0 parts by mass with respect to 100 parts by mass of the toner raw powder.

[Developer for developing electrostatic image]
The electrostatic image developing toner according to the present invention can be used alone as a one-component developer, or mixed with a carrier as a two-component developer. That is, the one-component developer is an electrostatic image developing developer containing the electrostatic image developing toner having the above-described configuration, and the two-component developer is an electrostatic image developing toner having the above-described configuration and a carrier. It is a developer for developing a charge image. Hereinafter, the description will focus on the two-component developer, but the one-component developer also conforms to the following description.

<Career>
In the present invention, any carrier that has been conventionally used as a carrier for two-component developers can be used without any particular limitation. As a specific example, for example, a carrier core material whose surface is coated with a resin can be used.

  Examples of the carrier core material include magnetic metals such as iron, nickel, and cobalt, alloys thereof, alloys containing rare earths, hematite, magnetite, manganese-zinc ferrite, nickel-zinc ferrite, manganese-magnesium. Magnetic particles produced by sintering and atomizing magnetic materials such as soft ferrites such as ferrite and lithium ferrite, iron oxides such as copper-zinc ferrite, and mixtures thereof. .

  Examples of the resin for covering the surface of the carrier core material include polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, tetrafluoroethylene / hexafluoropropylene copolymer (FEP), and tetrafluoroethylene. In addition to fluororesin such as perfluoroalkoxyethylene copolymer (PFA), polyamideimide resin, acrylic resin, straight silicon, etc. can be used.

The particle diameter of the carrier is 20 to 100 μm, more preferably 25 to 80 μm, still more preferably 30 to 60 μm, as measured by electron microscopy. The apparent specific gravity of the carrier varies depending on the composition of the magnetic material, the surface structure, and the like, but is generally preferably in the range of 3000 to 8000 kg / m ³ .

  The two-component developer can be produced by mixing the toner and the carrier in a dry manner using, for example, a ball mill. The toner concentration in the two-component developer is 3 to 20% by mass, more preferably 5 to 16% by mass, and still more preferably 8 to 12% by mass. When the toner density is less than 3% by mass, the image density tends to be excessively thin. On the other hand, when the toner concentration exceeds 20% by mass, toner scattering from the developing device occurs during operation of the image forming apparatus, and there is a tendency for fogging and contamination in the image forming apparatus to increase.

[Image forming apparatus]
In the image forming apparatus according to the present invention, the electrostatic image developing toner having the above configuration is used alone as a one-component developer, or the electrostatic image developing toner having the above configuration is mixed with a carrier as a two-component developer. This is the configuration to use. An image forming apparatus generally includes a photosensitive drum (image carrier) on which an electrostatic charge image (electrostatic latent image) is formed on a peripheral surface, and a developing device that develops the electrostatic charge image on the photosensitive drum using toner. With. In the present invention, the toner is an electrostatic charge image developing toner having the above configuration.

  A charging device, an exposure device, a developing device, a transfer device, and a cleaning device are disposed around the photosensitive drum.

  As the photosensitive drum, an organic photosensitive member (OPC) or an amorphous silicon photosensitive member is used. The charging device applies a predetermined potential to the peripheral surface of the photosensitive drum by generating corona discharge. The exposure apparatus selectively attenuates the potential of the peripheral surface of the photosensitive drum by irradiating light based on the image data to form an electrostatic charge image. The developing device forms a toner image by developing the electrostatic image formed on the peripheral surface of the photosensitive drum with toner. The transfer device transfers the toner image formed on the photosensitive drum onto the paper. The cleaning device removes the toner remaining on the peripheral surface of the photosensitive drum after the toner image is transferred onto the paper.

  The image forming apparatus further includes a fixing device having a heating roller and a pressure roller. The fixing device fixes the toner image on the paper by heating and pressurizing the paper on which the toner image is transferred.

  In the case of a two-component developer, the developing device includes a housing that contains a two-component developer including toner and a carrier, a stirring roller, a magnetic roller, and a developing roller (toner carrier) that are rotatably provided in the housing. And have.

The stirring roller charges the newly supplied toner by stirring it with the carrier and uniformly disperses it in the two-component developer. The magnetic roller carries the two-component developer supplied from the stirring roller as a magnetic brush on the peripheral surface. A control blade for controlling the thickness of the magnetic brush on the magnetic roller is disposed around the magnetic roller. The developing roller is disposed in the vicinity of the magnetic roller, and only the toner moves from the magnetic brush on the magnetic roller to the peripheral surface, so that a thin toner layer is formed on the peripheral surface. Further, the developing roller is disposed opposite to the photosensitive drum by a predetermined distance, and the electrostatic charge image on the photosensitive drum is visualized by moving the toner from the toner thin layer on the peripheral surface of the developing roller onto the photosensitive drum. Turn into. “Movement” here refers to the fact that the peripheral surface of the developing roller and the peripheral surface of the photosensitive drum are separated from each other, and the toner flies from the peripheral surface of the developing roller to the peripheral surface of the photosensitive drum (touch down method). It is a concept that includes.

  The outermost surface of the developing roller on which the toner thin layer is formed on the peripheral surface is constituted by a rotating developing sleeve. This developing sleeve is made of aluminum or SUS having uniform conductivity, and the surface is treated with an oxide film such as alumite or coated with a resin such as urethane or nylon to increase the surface resistance. Composed. By such a surface treatment of the developing sleeve, an appropriate electric resistance can be imparted, and good developing performance is realized while avoiding leakage. There is also an advantage that the adhesion force of the toner can be adjusted to a desired range by adjusting the surface roughness.

  However, if the surface of the developing sleeve is coated with resin, the resin fine particles detached from the toner raw powder are likely to adhere to the surface of the developing sleeve, and further, it is easy to adhere to the surface of the developing sleeve with the heat in the image forming apparatus. Become. As a result, it becomes difficult to control the thickness of the toner thin layer, which increases the possibility of causing image defects. Under such circumstances, in the present invention, the fixing of the resin fine particles to the toner raw powder is promoted, and the resin fine particles are less likely to be detached from the toner raw powder. This effect is very large.

  The image forming apparatus may be for a one-component developer. Further, a tandem color image forming apparatus having an intermediate transfer belt on which toner images of respective colors are superimposed on each other before the color image is transferred onto the paper may be used.

  Hereinafter, the present invention will be described in more detail through examples. In addition, this invention is not limited at all by this Example.

[Manufacture of developer]
(Production of silica A: hydrophobization treatment)
100 g of dimethylpolysiloxane and 100 g of 3-aminopropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) were dissolved in 200 g of toluene, and this solution was further diluted 10 times with toluene. Next, while stirring 200 g of hydrophilic fumed silica (“Aerosil (registered trademark) 90” manufactured by Nippon Aerosil Co., Ltd.), the diluted solution was gradually added dropwise thereto, followed by further stirring by ultrasonic irradiation for 30 minutes. To obtain a mixture. This mixture was heated using a high-temperature bath at 150 ° C., and then toluene was distilled off using a rotary evaporator, and the resulting solid was dried using a vacuum dryer at a set temperature of 50 ° C. until it was not reduced. Furthermore, heat treatment was performed at 200 ° C. for 3 hours under a nitrogen stream using an electric furnace. The obtained powder was crushed using a jet mill and collected using a bag filter to obtain silica A having a number average primary particle size of 20 nm.

(Production of titania A: hydrophobic treatment)
Titania A was obtained in the same manner as silica A except that 500 g of hydrophilic titania (“MT-150W” manufactured by Teica Co., Ltd .: primary particle diameter 15 nm) was used instead of 200 g of hydrophilic fumed silica.

(Production of titania B: hydrophobic treatment)
Titania B was obtained in the same manner as Titania A, except that 1000 g of hydrophilic titania (“MT-500B” manufactured by Teica Co., Ltd .: primary particle diameter 35 nm) was used instead of 500 g of hydrophilic titania “MT-150W”. It was.

(Production of titania C: hydrophobic treatment)
Titania C was obtained in the same manner as Titania A except that 1500 g of hydrophilic titania (“MT-600B” manufactured by Teica Co., Ltd .: primary particle diameter 50 nm) was used instead of 500 g of hydrophilic titania “MT-150W”. It was.

(Production of titania D: hydrophobic treatment)
Titania D is the same as Titania A except that 3000 g of hydrophilic titania (“TAF-520” manufactured by Fuji Titanium Industry Co., Ltd .: primary particle diameter 100 nm) is used instead of 500 g of hydrophilic titania “MT-150W”. Got.

(Preparation of titania composite resin fine particles A)
100 g of negatively charged acrylic polymer resin fine particles (“MG-151” manufactured by Nippon Paint Co., Ltd .: primary particle diameter 70 nm) and 100 g of titania A were introduced into a mechanical composite device (“Nobilta NOB-130” manufactured by Hosokawa Micron Co., Ltd.) at 1500 rpm. The titania composite resin fine particles A were obtained by treating at a rotational speed of 5 minutes for 5 minutes.

(Preparation of titania composite resin fine particles B)
A titania composite resin fine particle B was obtained in the same manner as the titania composite resin fine particle A, except that 100 g of titania B was used instead of the titania A 100 g and the rotation speed of the mechanical composite device was changed to 3000 rpm.

(Preparation of titania composite resin fine particles C)
Instead of 100 g of resin fine particles “MG-151”, 100 g of resin particles of negatively chargeable acrylic polymer (“N-474” manufactured by Nippon Paint Co., Ltd .: primary particle diameter 160 nm) are used, and the rotational speed of the mechanical compounding device is 3000 rpm. Otherwise, titania composite resin fine particles C were obtained in the same manner as titania composite resin fine particles A.

(Preparation of titania composite resin fine particles D)
A titania composite resin fine particle D was obtained in the same manner as the titania composite resin fine particle A except that the amount of titania A input was changed to 60 g.

(Preparation of titania composite resin fine particles E)
Titania composite resin fine particles E were obtained in the same manner as the titania composite resin fine particles A except that the input amount of titania A was changed to 140 g.

(Preparation of titania composite resin fine particles F)
The titania composite resin fine particle F is the same as the titania composite resin fine particle A except that the titania C 100 g is used instead of the titania A 100 g, the rotational speed of the mechanical composite device is changed to 3000 rpm, and the processing time is changed to 10 minutes. Got.

(Preparation of titania composite resin fine particles G)
Titania composite resin fine particles G were obtained in the same manner as the titania composite resin fine particles A except that the input amount of titania A was changed to 50 g.

(Preparation of titania composite resin fine particles H)
Titania composite resin fine particles H were obtained in the same manner as the titania composite resin fine particles A except that the amount of titania A input was changed to 150 g.

(Preparation of titania composite resin fine particles I)
Instead of 100 g of resin fine particles “MG-151”, 100 g of resin fine particles of negatively chargeable styrene-acrylic polymer (“MG-154” manufactured by Nippon Paint Co., Ltd .: primary particle diameter 300 nm) were used. In the same manner as A, titania composite resin fine particles I were obtained.

(Preparation of titania composite resin fine particles J)
In place of 100 g of resin fine particles “MG-151”, 100 g of resin particles of positively chargeable acrylic polymer (“MG-152” manufactured by Nippon Paint Co., Ltd .: primary particle diameter 70 nm) were used. Similarly, titania composite resin fine particles J were obtained.

(Preparation of titania composite resin fine particles K)
Titania composite resin fine particles K were obtained in the same manner as the titania composite resin fine particles A except that 100 g of titania D was used instead of 100 g of titania A.

(Preparation of toner raw powder A)
100 parts by mass of a positively chargeable polyester resin as a binder resin, 8 parts by mass of carbon black as a colorant, 5 parts by mass of a release agent, and 1 part by mass of a charge control agent are put into a Henschel mixer and mixed. It was melt-kneaded with an extruder and cooled with a drum flaker. The obtained solid is coarsely pulverized with a hammer mill, then finely pulverized with a turbo mill, and classified using an air classifier, and the toner raw powder having a volume average particle size of 6.81 μm and an average circularity of 0.951. A was obtained.

(Preparation of carrier A)
After 30 g of the polyamideimide resin was diluted with 2 L of water, 120 g of tetrafluoroethylene / hexafluoropropylene copolymer (FEP) was dispersed, and 3 g of silicon oxide was further dispersed to obtain a coating layer forming liquid. The coating layer forming solution and 10 kg of non-coated ferrite (“EF-35B” manufactured by Powdertech Co., Ltd .: particle diameter 35 μm) were put into a fluidized bed coating apparatus to perform coating, followed by baking at 250 ° C. for 1 hour. Carrier A was obtained.

(Preparation of toners A to K)
2 kg of toner raw powder A, 40 g of silica A, and 20 g of titania composite resin fine particles A to K were put into a Henschel mixer and stirred and mixed at 40 m / s for 5 minutes to obtain toners A to K.

(Preparation of Toner L)
Toner L was obtained in the same manner as Toner A, except that 20 g of resin fine particles “MG-151” were used instead of 20 g of titania composite resin fine particles A to K.

(Preparation of Toner M)
Toner M was obtained in the same manner as toner A except that titania A20 g was used instead of titania composite resin fine particles A to K20 g.

(Preparation of developers A to M)
Developers A to M were obtained by uniformly stirring and mixing toner A to M 30 g and carrier A 300 g with a ball mill for 30 minutes.

  Table 1 summarizes the features of the developers A to M manufactured as described above. Developers A to I are examples that fall within the scope of the present invention, developers J to L are comparative examples, and developer M is a reference example.

[Developer evaluation]
Developers A to M were mounted on a digital color multifunction printer (trade name “TASKalfa500ci”) manufactured by Kyocera Mita Corporation, and the following evaluation was performed.

(Image density)
The image density at the time of continuously printing 3000 images with a printing rate of 0.2% on PPC paper was measured using a spectroeye reflection densitometer manufactured by Gretag Macbeth. An image density of 1.2 or higher is accepted.

(Cover)
Print 3000 sheets of images with a printing rate of 0.2% continuously on PPC paper, and then use a spectro-eye reflection densitometer made by Gretag Macbeth to measure the density (fogging) of the white paper when printing an image with a printing rate of 20%. And measured. A fog of 0.008 or less is accepted.

  Here, the reason why printing with a high printing rate (20%) was performed after printing with a low printing rate (0.2%) for a long time was to create a situation in which fogging was likely to occur. In other words, when printing with a low printing rate is performed for a long time, a large amount of toner is subjected to thermal stress and mechanical stress without being used for a long time. The state of the toner surface may change due to the burying of the toner, and the charging ability of the toner may be reduced. When high-printing printing starts, the amount of new toner that has not been stressed and charging capacity has not increased will increase, so charge transfer from old toner with low charging capacity to new toner with high charging capacity will occur. Occurs, and the charge amount of the older toner decreases. As a result, fog due to the toner having a further reduced charge amount is likely to occur. As described above, when resin fine particles are used as an external additive, the resin fine particles are close to the binder resin of the toner raw powder and the triboelectric charge series, so even if subjected to thermal stress or mechanical stress, Even if the toner is buried, a decrease in charging ability of the toner is suppressed, and toner charging failure is suppressed.

(Amount of scattered toner)
The amount of toner deposited on the developing jaw at the time when 3000 images of a printing rate of 20% were continuously printed was measured. A toner amount of less than 50 mg is considered acceptable.

(Career spent amount)
The toner from the developer at the time when 300,000 sheets of an image with a printing rate of 5% were continuously printed was removed by suction with a vacuum cleaner through a 635 mesh sieve, and the carbon content of the separated carrier was measured using a carbon analyzer “EMIA-” manufactured by Horiba. 110 ". A carbon content of less than 2% is considered acceptable. In this test, the amount of the resin fine particles detached from the toner raw powder adhered to the carrier is measured.

(Development sleeve surface resistance)
The surface resistance of the central portion of the developing sleeve at the time when 300,000 images with a printing rate of 5% were continuously printed was measured with a high resistivity measuring device “HIRESTA MCP-HT450” manufactured by Mitsubishi Chemical Co., Ltd. with 1000 V applied. A surface resistance of less than 1 × 10 ¹⁰ Ω is accepted. In this test, the degree of the amount of resin fine particles detached from the toner raw powder adhered to the surface of the developing sleeve and melted and fixed is measured. The greater the amount of resin fine particles fixed, the higher the surface resistance, leading to image defects.

  Table 2 summarizes the results of the evaluation performed as described above.

  As is apparent from Table 2, the chargeability (negative chargeability) of the resin fine particles is opposite in polarity to the chargeability (positive chargeability) of the toner raw powder, and the resin fine particles are combined with inorganic fine particles. Developers A to I (Examples) in which the particle size of the inorganic fine particles is smaller than the particle size of the toners have good evaluation results in all points of image density, fogging, scattered toner amount, carrier spent amount, and developing sleeve surface resistance. Met.

  On the other hand, developer J (comparative example) in which the chargeability (positive chargeability) of the resin fine particles is the same polarity as the chargeability (positive chargeability) of the toner raw powder is evaluated in terms of fog and scattered toner amount. The result was inferior. This is because the resin fine particles have sufficient characteristics that the fixing of the resin fine particles to the toner raw powder is not electrostatically promoted, the resin fine particles are easily detached from the toner raw powder, and the toner is excellent in suppressing poor charging. It is considered that it was not demonstrated. Further, the positively chargeable resin mother particles tend to gradually decrease in the positive chargeability, and the fact that the decrease in the positive chargeability of silica cannot be compensated is considered as a cause of fogging. In other words, the negatively chargeable resin fine particles are effective in fogging because the positive chargeability increases with mixing. Since the change in the charge amount is opposite to the tendency of silica to decrease in charge, the effect of suppressing charging failure can be obtained. On the other hand, the positively chargeable resin fine particles are positively charged from the start of mixing, and there is no change that the positive chargeability increases with mixing.

  In addition, the developer K (comparative example) in which the particle size of the inorganic fine particles is larger than the particle size of the resin fine particles was also inferior in evaluation results in terms of fog and scattered toner amount. It is considered that this is because the main component of the composite particles is inorganic fine particles, and the characteristics of the resin fine particles that are excellent in suppressing toner charging failure are not sufficiently exhibited.

  In addition, the developer L (comparative example) using resin fine particles in which inorganic fine particles are not combined is also inferior in evaluation results in terms of fog and scattered toner amount. This is because the specific gravity of the resin fine particles does not increase, the fixing of the resin fine particles to the toner raw powder is not promoted, the resin fine particles are easily detached from the toner raw powder, and the resin fine particles are excellent in suppressing poor charging of the toner. It is considered that this characteristic was not fully exhibited. Further, it is considered that the resin fine particles detached from the toner raw powder contaminated the toner carrier such as the developing sleeve, the photosensitive drum, or the carrier.

  In addition, the developer M (comparative example) in which resin fine particles are not used was remarkably inferior to the other developers A to L in terms of image density, fog, and scattered toner amount. The reason why the evaluation results of the carrier spent amount and the developing sleeve surface resistance are comparatively good is that the developer M does not use resin fine particles that deteriorate the evaluation results of the carrier spent amount and the developing sleeve surface resistance.

Claims (8)

An electrostatic charge image developing toner in which an external additive is added to a toner raw powder,
The external additive includes resin fine particles having chargeability opposite to that of the toner raw powder,
An electrostatic charge image developing toner, wherein resin fine particles are combined with inorganic fine particles having a particle diameter smaller than that of the resin fine particles.   2. The electrostatic image developing toner according to claim 1, wherein the resin fine particles are at least one selected from the group consisting of an acrylic copolymer, an acrylic homopolymer, a methacrylic copolymer, and a methacrylic homopolymer.   The electrostatic image developing toner according to claim 1, wherein the inorganic fine particles are at least one selected from the group consisting of silica, alumina, and titania.   The electrostatic image developing toner according to claim 1, wherein the resin fine particles have a particle size of 70 to 300 nm and the inorganic fine particles have a particle size of 15 to 50 nm.   The toner for developing an electrostatic charge image according to any one of claims 1 to 4, wherein a blending amount of the inorganic fine particles is 50 to 150 parts by mass with respect to 100 parts by mass of the resin fine particles.   The electrostatic image developing toner according to claim 1, wherein the toner is used for an image forming apparatus including a developing sleeve having a surface coated with a resin.   An electrostatic charge image developing developer comprising the electrostatic charge image developing toner according to claim 1 and a carrier.   An image forming apparatus using the electrostatic image developing toner according to claim 1 or the electrostatic image developing developer according to claim 7.