JP4871184B2 - Method for producing carrier for developing electrostatic latent image, carrier produced by the production method, developer using the carrier, and image forming method using the developer - Google Patents

Description

  The present invention relates to a method for producing a carrier for developing an electrostatic latent image suitably used in electrophotography, electrostatic recording method, electrostatic printing method, etc., a carrier produced by the production method, and development using the carrier The present invention relates to an agent and an image forming method using the developer.

  The dry development method used in electrophotography forms a visible image by electrostatically attaching toner rubbed with a charging member to an electrostatic latent image. In such a dry development method, a so-called one-component development method having toner as a main component, glass beads, a magnetic carrier, or a carrier whose surface is coated with a resin and the toner are mixed. There is a so-called two-component development system to be used.

  In the developer used in the two-component development system, minute toner particles are held on the surface of a relatively large core material by the electric force generated by friction between both particles, and this developer is close to the electrostatic latent image. Then, the toner particles overcome the binding force with the core material by the electric field formed by the electrostatic latent image, and are developed on the electrostatic latent image. The developer is repeatedly used while replenishing the toner consumed by the development.

  For this reason, the core material must be triboelectrically charged with a desired polarity and a sufficient charge amount at all times during long-time use. However, collision between the particles, mechanical stirring in the particles and the developing device, or heat generated by them generates a so-called spent toner in which the toner is fused to the surface of the core material, and the charging characteristics of the core material decrease with use time. To do. As a result, the background of the image and toner scattering occur, so that the entire developer needs to be replaced.

  In order to prevent such spending, the life of the carrier is extended by coating the surface of the core material with a resin having a low surface energy, such as a fluororesin or a silicone resin. For example, a carrier coated with a room temperature curable silicone resin and a positively chargeable nitrogen resin (see Patent Document 1), a carrier coated with a coating material containing at least one modified silicone resin (see Patent Document 2), a room temperature curable silicone A carrier having a coating layer containing a resin and a styrene-acrylic resin (see Patent Document 3), a carrier in which the core particle surface is coated with two or more layers of silicone resin so that there is no adhesion between the layers (see Patent Document 4) ), A carrier in which silicone resin is applied in multiple layers on the core particle surface (see Patent Document 5), a carrier whose surface is coated with a silicon resin containing silicon carbide (see Patent Document 6), and exhibits a critical surface tension of 20 dyn / cm or less. A positively chargeable carrier coated with a material (see Patent Document 7) and coated with a coating material containing a fluorine alkyl acrylate. And a carrier, the developer comprising a toner containing a containing chromium azo dye (see Patent Document 8), and the like.

  Recently, in order to improve image quality, the toner tends to have a smaller particle size, and as a result, toner spent on the carrier is likely to occur. In addition, in conventional spray coating, it is difficult to uniformly wet the carrier surface with a coating material, and therefore it is difficult to produce a carrier having a coating film and a core material with a uniform film thickness and film quality. It has become. Furthermore, in the case of a full color toner, a resin with a low softening point is used in order to obtain a sufficient color tone. Therefore, the spent amount to the carrier is larger than that of the black toner, and the toner charge amount is reduced. Scattering and background contamination occur. As described above, in the full-color electrophotographic system, when the toner charge amount is lowered, there is a problem that the image density particularly in the highlight portion is easily changed and the high image quality cannot be maintained.

  In addition, in order to improve the durability of the carrier, a coating layer in which fine particles and a conductivity-imparting material are dispersed in a resin matrix of a low surface energy substance can be provided to control the spent resistance, film strength, and electrical characteristics. Although shown (see Patent Documents 9 to 11), since a dispersion liquid in which fine particles are added to an organic solvent is spray-coated at a high temperature, there is a problem that it is difficult to make the charge amount uniform due to aggregation of the fine particles and the like.

  Conventional spray coating also has manufacturing problems such as regulation of volatile organic compounds (VOC) by organic solvents used when forming a coating layer on the surface of the core material, generation of waste liquid, and the need for drying energy. Yes.

  In order to solve these problems, as a carrier production method using a dry powder process that does not use an organic solvent, there is a carrier particle production method using a supercritical fluid (see Patent Document 12). The content is that the coating resin is melted and coated in a heated state, and since the resin material is an acrylic resin, the aforementioned problem of spent is not solved.

  Further, in the method for producing a carrier using a supercritical fluid described in Patent Document 13, a silicone resin is used as a coating material. However, since the solubility in the supercritical fluid is insufficient, plasticization and fine dispersion are performed. The resulting silicone resin is sprayed simultaneously with the core material to coat the surface of the core material. For this reason, the film thickness of the obtained coating film is poor in uniformity, and a coating film sufficient to satisfy the durability cannot be formed. Further, in this manufacturing method, a step of dispersing the conductivity imparting material in the resin matrix is provided, but due to dispersion by kneading, fine dispersion is insufficient, and the problem of non-uniform composition due to the aggregation or the like is It cannot be solved.

Therefore, a carrier having a coating layer on the surface of the core material, in which the fine particles are uniformly dispersed in the coating layer, the adhesive property between the core material and the fine particles, the coating layer is high, and the coating layer having a uniform thickness is sufficient. There is no technology that can satisfy these requirements. Furthermore, from the viewpoint of environmental load and resource saving, there are many problems to be improved in the conventional carrier manufacturing method and carrier.
Japanese Patent Laid-Open No. 55-127469 Japanese Patent Laid-Open No. 55-157751 JP-A-56-140358 JP-A-57-96355 JP 57-96356 A JP 58-207054 A JP-A-61-1110161 JP-A-62-273576 JP-A-9-319161 JP-A-9-269614 Japanese Patent Laid-Open No. 10-186731 US Pat. No. 5,514,512 JP 2006-106208 A

  An object of the present invention is to solve the above-described conventional problems and achieve the following object. That is, the present invention has a coating layer on the surface of the core material, the fine particles are uniformly dispersed in the coating layer, the adhesive property between the core material, the fine particles, and the coating layer is high, and the coating layer has a uniform thickness. Production method of carrier for developing electrostatic latent image, carrier produced by the production method, developer using the carrier without toner scattering and background contamination, and image using the developer An object is to provide a forming method.

  In order to solve the above-mentioned problems, the invention according to claim 1 is a method for manufacturing a carrier having a coating layer formed on the surface of a core material, wherein the core material and the fine particles are mixed to obtain a mixture of the core material and the fine particles. And a step of mixing the mixture and the coating resin in a supercritical fluid or a subcritical fluid to form a coating layer on the surface of the mixture.

  According to a second aspect of the present invention, in the carrier manufacturing method according to the first aspect, the fine particles are fixed on the surface of the core material.

  According to a third aspect of the present invention, in the method for producing a carrier according to the first or second aspect, the mixture is formed by a mechanochemical method.

  According to a fourth aspect of the present invention, in the method for producing a carrier for developing an electrostatic latent image according to the first aspect, the coating layer is formed by controlling the pressure or temperature of the supercritical fluid or subcritical fluid. It is characterized by that.

  The invention according to claim 5 is the method for producing a carrier for developing an electrostatic latent image according to claim 1 or 4, wherein the supercritical fluid or subcritical fluid is carbon dioxide.

  A sixth aspect of the present invention is the method for producing a carrier for developing an electrostatic latent image according to any one of the first to fifth aspects, wherein the fine particles are made of a material having a composition different from that of the coating layer. .

  According to a seventh aspect of the present invention, in the method for producing a carrier for developing an electrostatic latent image according to any one of the first to sixth aspects, the fine particles are a metal oxide.

  The invention according to claim 8 is the method for producing a carrier for developing an electrostatic latent image according to any one of claims 1 to 7, wherein the core material has a volume average particle diameter in the range of 20 to 50 μm. It is characterized by.

  The invention described in claim 9 is characterized by an electrostatic latent image developing carrier manufactured by the manufacturing method according to any one of claims 1 to 8.

  The invention described in claim 10 is characterized in that the carrier described in claim 9 is mixed with a developer.

  According to an eleventh aspect of the present invention, there is provided an electrostatic latent image forming step of forming an electrostatic latent image on an electrostatic latent image carrier, and developing the electrostatic latent image using a developer to form a visible image. An image forming method including at least a developing step, a transferring step of transferring the visible image onto a recording medium, and a fixing step of fixing the transferred image transferred onto the recording medium, wherein the developer is claimed in claim 10. It is a developing agent as described in above.

  The carrier production method of the present invention comprises a step of mixing a core material and fine particles to uniformly disperse the fine particles on the surface of the core material, and mixing the mixture and resin in a supercritical fluid or subcritical fluid. A step of forming a coating layer on the surface, so that the dispersibility of the fine particles is improved, the adhesiveness between the core material and the fine particles, the core material and the coating layer is high, and a uniform thickness coating layer is obtained. In addition, it can efficiently produce a carrier having high mechanical strength, excellent toner chargeability and stability over time, and not only can the regulations of volatile organic compounds (VOC) be cleared, but also no waste liquid is generated. It can be produced with little need for drying energy.

  In addition, it is possible to provide a developer that can form an image with a high image density without using toner scattering and background contamination, and an image forming method using the developer.

Hereinafter, the present invention will be described in detail.
As described above, the present invention provides a method for producing a carrier having a coating layer formed on the surface of a core material, the step of mixing the core material and the fine particles to form a mixture of the core material and the fine particles, and the mixture. And a coating resin in a supercritical fluid or a subcritical fluid to form a coating layer on the surface of the mixture, and a method for producing a carrier for developing an electrostatic latent image.
The coating layer may be formed by coating with an organic solvent, but when an organic solvent is used, aggregation of fine particles occurs due to liquid crosslinking during solvent evaporation. On the other hand, when a supercritical fluid or a subcritical fluid is used, the interfacial tension is small and aggregation can be prevented.

  Thus, the present invention uses a supercritical fluid or a subcritical fluid as a solvent to form a coating layer on the surface of the core material, but before forming the coating layer on the surface of the core material, A material and fine particles are mixed to form a mixture of a core material and fine particles, and the fine particles are uniformly dispersed on the surface of the core material. Then, by forming a coating layer on the surface of the mixture of the core material and fine particles with a coating resin dissolved or dispersed in a supercritical fluid or subcritical fluid, the adhesion between the core material and the fine particles, and the core material and the coating layer is improved. A coating layer having a high and uniform thickness can be obtained, and a carrier having high mechanical strength can be obtained.

  In addition, according to the carrier production method of the present invention, volatile organic compound (VOC) regulations can be cleared, no waste liquid is generated, and almost no drying energy is required, and the carrier can be produced efficiently. In particular, supercritical carbon dioxide is nonflammable and highly safe, and can provide a carrier with a hydrophobic surface using a non-aqueous solvent. It can be recovered and reused easily because it is gasified just by returning to atmospheric pressure. The obtained carrier also has an excellent characteristic that drying is unnecessary.

  Hereinafter, an embodiment of a carrier manufacturing method of the present invention will be described with reference to the drawings.

<Formation of mixture of core material and fine particles>
−Core material−
The core material used in the present invention is not particularly limited, and can be appropriately selected according to the purpose from those known as two-component carriers for electrophotography. For example, ferrite, magnetite, iron, nickel can be used. Preferably mentioned. In addition, in consideration of the environmental aspects that have advanced remarkably in recent years, if ferrite is used, for example, Mn ferrite, Mn-Mg ferrite, Mn-Mg-Sr ferrite, etc. should be used instead of the conventional copper-zinc ferrite. Is preferred.

  The core material preferably has a volume average particle size of 20 μm or more from the viewpoint of prevention of carrier adhesion (scattering) to the electrostatic latent image carrier, and is intended to prevent deterioration of image quality such as prevention of occurrence of carrier streaks. To 100 [mu] m or less is preferable, and in particular, a volume average particle size of 20 to 50 [mu] m is more preferable for high image quality in recent years.

Here, the volume average particle diameter of the core material can be measured by using, for example, “Microtrac particle size analyzer SRA; manufactured by Nikkiso Co., Ltd.” with a range of 0.7 to 125 μm.
The specific surface area of the core material is preferably set as appropriate. For example, according to the BET method, nitrogen gas can be adsorbed on the sample surface using a “specific surface area measuring device Tristar 3000” (manufactured by Shimadzu Corporation), and measurement can be performed using the BET multipoint method.

-Fine particles-
The fine particles used in the present invention are not particularly limited, and for example, inorganic fine particles such as metal powder and various metal oxide particles are preferably used. Among them, metal oxide particles such as silicon oxide, titanium oxide, and alumina can easily obtain particles having a uniform fine particle diameter, and various electrical characteristics and mechanical strength can be obtained depending on the particles used. It is also important that the fine particles are thermally stable even when the carrier is heated to a high temperature during the condensation curing of the silicone resin.

  Further, it is particularly preferable that the fine particles are fine particles having a hardness higher than that of the silicone polymer constituting the outer shell. In this case, the coating layer of the carrier is a contact portion between the carrier and the carrier, between the carrier and the toner, and between the carrier and the member in the developing device. Since the core material is a hard magnetic powder, it is preferable that the fine particles have a high hardness as well. That is, grinding can be prevented by having a higher hardness than the silicone polymer. The above metal oxide particles are representative of high hardness particles.

For the purpose of the electric resistance adjusting material constituting the carrier surface, conductive ZnO, metal powder such as Al, SnO ₂ doped with SnO ₂ or various elements made by various methods; borides (e.g. TlB _{2, ZnB 2, MoB 2)} ; silicon carbide, conductive polymers (e.g. polyacetylene, polyparaphenylene, poly (para - phenylene sulfide), polypyrrole, parylene, etc.), may contain fine particles such as carbon black.

-Mixing method-
It is preferable to use a mechanochemical method to form a mixture of the core material and fine particles.
Here, the mechanochemical method is to perform compounding by applying mechanical energy to the powder particles, and for example, mixing is performed using a high-speed fluid mixer Supermixer SMP-2 manufactured by Kawata Corporation. be able to.

<Formation of coating layer>
Next, in order to form a coating layer on the surface of the mixture of core material and fine particles formed as described above, the mixture and coating resin are mixed in a supercritical fluid or a subcritical fluid to form a coating layer on the surface of the mixture. Let

-Supercritical fluid and subcritical fluid-
Supercritical fluid has properties that are intermediate between gas and liquid, and has properties such as mass transfer (as fast as liquid) and heat transfer (as liquid) and low viscosity (as gas). A fluid whose density, dielectric constant, solubility parameter, free volume, etc. can be changed continuously and greatly by changing temperature and pressure. Furthermore, since the supercritical fluid has an extremely small interfacial tension compared to an organic solvent, it can follow even a minute undulation (surface) and can be wetted (contacted with the supercritical fluid). .

  The supercritical fluid exists as a non-condensable high-density fluid in a temperature and pressure range that exceeds the limit (critical point) where gas and liquid can coexist, does not cause condensation even when compressed, and exceeds the critical temperature. And, as long as it is a fluid in a state of a critical pressure or higher, it can be used without any particular limitation.In the present invention, it can be appropriately selected according to the purpose, but those having a low critical temperature and critical pressure are preferred, The subcritical fluid can be used without particular limitation as long as it exists as a high-pressure liquid in the temperature and pressure regions near the critical point, and can be appropriately selected according to the purpose in the present invention.

  Examples of the supercritical fluid or subcritical fluid include carbon monoxide, carbon dioxide, ammonia, nitrogen, water, methanol, ethanol, ethane, propane, 2,3-dimethylbutane, benzene, chlorotrifluoromethane, and dimethyl ether. Is mentioned. Among these, carbon dioxide can easily be in a supercritical state with a critical pressure of 7.3 MPa and a critical temperature of 31 ° C., and is nonflammable and highly safe, and since it is a non-aqueous solvent, a carrier with a hydrophobic surface can be obtained. In addition, since it is gasified simply by returning to normal pressure (releasing the pressure), it can be easily recovered and reused. The obtained carrier does not need to be dried, and since it does not generate waste liquid, it is friendly to the global environment. preferable.

  The supercritical fluid or the subcritical fluid may be used alone or as a mixture of two or more. When two or more kinds are used in combination, it is only necessary to hold a supercritical fluid or a subcritical fluid.

  The critical temperature and critical pressure of the supercritical fluid are not particularly limited and may be appropriately selected depending on the intended purpose. However, the critical temperature is preferably −273 to 300 ° C., more preferably 0 to 200 ° C. preferable. The lower the critical pressure, the more advantageous, for example, in terms of apparatus load, equipment cost, operating energy, etc., but in practice, 1-100 MPa is preferable, and 1-50 MPa is more preferable.

  In the present invention, the coating layer can be formed on the surface of the mixture of the core material and the fine particles by positively utilizing the properties of the supercritical fluid or the subcritical fluid.

  In addition, since the supercritical fluid can be easily separated from the target product and can be recovered and reused, it is possible to realize an innovative carrier production method with low environmental load that does not use conventional water or organic solvents.

  In addition to the supercritical fluid or the subcritical fluid, other fluids can be used in combination. Such other fluid is preferably one that can easily control the solubility of the coating resin. Specifically, methane, ethane, propane, ethylene and the like are preferable. At this time, the solubility is controlled by controlling at least one of the conditions of pressure and temperature (pressure only, temperature only, or both pressure and temperature). For example, the pressure can be reduced to reduce the solubility.

  In addition to the supercritical fluid or the subcritical fluid, an entrainer (azeotropic agent) may be added. By adding this entrainer, the solubility of the coating resin can be improved. There is no restriction | limiting in particular as said entrainer, Although it can select suitably according to the objective, A polar organic solvent is preferable. Examples of the polar organic solvent include methanol, ethanol, propanol, butanol, hexane, toluene, ethyl acetate, chloroform, dichloromethane, ammonia, melamine, urea, thioethylene glycol, and the like. Among these, lower alcohol solvents having about 1 to 6 carbon atoms (preferably about 1 to 4 carbon atoms) exhibiting poor solvent properties at normal temperature and normal pressure are suitable.

-Resin for coating-
The coating resin is not particularly limited and may be appropriately selected from known resins according to the purpose. Examples thereof include amino resins, polyvinyl resins, polystyrene resins, halogenated olefin resins, and polyesters. Resin, polycarbonate resin, polyethylene resin, polyvinyl fluoride resin, polyvinylidene fluoride resin, polytrifluoroethylene resin, polyhexafluoropropylene resin, copolymer of vinylidene fluoride and acrylic monomer, vinylidene fluoride and Copolymers with vinyl fluoride, fluoroterpolymers (triple fluoride (multiple) copolymer) such as terpolymers of tetrafluoroethylene, vinylidene fluoride and non-fluorinated monomers, silicone resins, etc. . These may be used individually by 1 type and may use 2 or more types together. Among these, a silicone resin is particularly preferable because of its high effect.

  There is no restriction | limiting in particular as said silicone resin, Although it can select suitably according to the objective from generally known silicone resins, For example, the straight silicone resin represented by following Structural formula (i) Is preferred.

  In the structural formula (i), R represents a hydrogen atom, a hydroxyl group, an alkoxy group, an alkyl group, or an aryl group. Examples of the alkoxy group include a methoxy group and an ethoxy group. Examples of the alkyl group include a methyl group, an ethyl group, and a propyl group. Examples of the aryl group include a phenyl group, a tolyl group, and a xylyl group.

  The weight average molecular weight (Mw) of the silicone resin as a coating resin that can be used in the present invention is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 500 to 100,000, preferably 1,000 to 40,000 is more preferable.

  Further, the silicone resin as the coating resin is preferably a solid at 25 ° C. and normal pressure from the viewpoint of superior handling property, film formability, and film thickness controllability than liquid. Here, the normal pressure refers to a pressure in a standard state, and is 0.1 MPa in the present invention.

The molecular weight can be measured by the following method.
Gel permeation chromatography (GPC) measuring device: GPC-8220 GPC (manufactured by Tosoh Corporation)
・ Column: TSKgel SuperHZM-H 15cm triple (manufactured by Tosoh Corporation)
・ Temperature: 40 ℃
・ Solvent: THF
・ Flow rate: 0.35 ml / min
-Sample: 0.4 ml of 0.15% sample was injected-Sample pretreatment: The toner was dissolved in tetrahydrofuran THF (made by Wako Pure Chemical Industries, Ltd.) at 0.15 wt% and filtered through a 0.2 μm filter. The filtrate is used as a sample. 100 μl of the THF sample solution is injected and measured. In measuring the molecular weight of a sample, the molecular weight distribution of the sample is calculated from the relationship between the logarithmic value of a calibration curve prepared from several types of monodisperse polystyrene standard samples and the number of counts. As a standard polystyrene sample for preparing a calibration curve, Showd STANDARD Std. No S-7300, S-210, S-390, S-875, S-1980, S-10.9, S-629, S-3.0, S-0.580, and toluene were used. An RI (refractive index) detector was used as the detector.

As described above, the silicone resin as the coating resin is preferably a solid at room temperature and normal pressure because it is superior in handling property, film formability and film thickness controllability than liquid.
The silanol concentration of the silicone resin as a coating resin that can be used in the present invention is preferably 1 to 40% by mass, more preferably 1 to 20% by mass, and still more preferably 1 to 10% by mass for crosslinking after film formation. . When the silanol concentration exceeds 40% by mass, the crosslinked film tends to be hard and brittle, the durability is deteriorated, and unreacted silanol groups remain, so that the environmental stability of the carrier is deteriorated. is there. If it is less than 1%, the coating performance as a coating resin may be inferior.

  As said silicone resin, what was synthesize | combined suitably may be used and a commercial item may be used. Examples of the commercially available products include KR271, KR255, KR220L, and KR152 manufactured by Shin-Etsu Chemical Co., Ltd .; SR2400, SR2406, SR2410, SR213, 217 Flakes Resin, 220 Flakes Resin, and 233 manufactured by Toray Dow Corning. Flakes Resin, 249 Flakes Resin, Z-6018 Intermediate, and the like.

  Examples of the modified silicone resin include KR206 (alkyd modified), KR5208 (acrylic modified), ES1001N (epoxy modified), KR305 (urethane modified) manufactured by Shin-Etsu Chemical Co., Ltd .; SR2115 (manufactured by Toray Dow Corning). Epoxy modified), SR2110 (alkyd modified), and the like.

  The silicone resin can be used alone, but a component that undergoes a crosslinking reaction, a charge amount adjusting component, and the like can also be used at the same time.

  When the carrier thus obtained is used as a two-component developer, it is preferable that the LogR of the measured electric resistance is in the range of 7 to 16 Ωcm. The electrical resistance can be appropriately selected according to the development process using the carrier. When LogR is less than 7, the spike shape of the carrier brush (magnetic brush) held on the developer carrying member has an image density. When the LogR exceeds 16 Ωcm, a difference in density between the edge portion of the image and a solid portion or a difference in density between the line image and the solid image may occur. Problems such as a decrease in capability and carrier development (carrier adhesion) on the non-image portion of the latent image are likely to occur.

  The electric resistance of the carrier is a value obtained from a current value and an applied voltage when a carrier is filled between two parallel electrodes and a potential difference is provided between the electrodes. Specifically, a container having electrodes arranged in parallel at an interval of 2 mm is filled with a carrier, and a direct current resistance at a potential difference of 500 V between the two electrodes is measured with a 4329A High Resistance Meter manufactured by Yokogawa Hewlett-Packard Co., Ltd.

  For the same reason, the thickness of the carrier film is preferably set as appropriate so that the electric resistance is within an appropriate range. However, as silicone has a volume shrinkage during the condensation reaction, the film thickness increases. , There is a drawback that non-uniform reaction within the film tends to occur. Therefore, the film thickness is more preferably 1.0 μm or less.

  The method for forming the coating layer is not particularly limited as long as the coating resin is dissolved or dispersed in the fluid containing the supercritical fluid or the subcritical fluid, and can be appropriately selected depending on the purpose.

  An apparatus for forming the coating layer is not particularly limited and may be appropriately selected depending on the intended purpose. For example, a pressure-resistant container for dissolving or dispersing at least the coating resin, and the supercritical fluid The apparatus provided with the pressurization pump which supplies is mentioned suitably. As a processing method using the apparatus, first, a coating resin, a mixture of the core material and fine particles described above is charged into the pressure vessel, and the supercritical fluid is supplied into the pressure vessel by a pressure pump, The supercritical fluid is brought into contact with the resin for resin and the mixture to form a coating layer on the surface of the mixture. When the supercritical fluid is returned to normal temperature and normal pressure, the supercritical fluid becomes a gas, so that removal of the solvent is unnecessary and waste water generated by washing is unnecessary, reducing the environmental load. The

  The temperature at which the coating layer is formed on the surface of the mixture is not particularly limited as long as it is equal to or higher than the critical temperature of the supercritical fluid or the subcritical fluid to be used, and can be appropriately selected according to the purpose. Specifically, 0 to 100 ° C. is preferable, and 20 to 80 ° C. is more preferable. When the said temperature exceeds 100 degreeC, a core material may melt | dissolve.

  The pressure for forming the coating layer on the surface of the mixture is not particularly limited as long as it is equal to or higher than the critical pressure of the supercritical fluid or the subcritical fluid to be used, and can be appropriately selected according to the purpose. 1-60 MPa is preferable.

  Specifically, a coating layer can be formed on the surface of the mixture using the apparatus shown in FIG. In the carrier processing tank of the apparatus of FIG. 1, the coating resin and the mixture are charged, the valve 3 is opened while stirring, carbon dioxide is supplied by the pressure pump 2 to 25 MPa and 40 ° C., and then the valve 3 is turned on. Closed. After maintaining the inside of the carrier treatment tank at 25 MPa and 40 ° C. for 2 hours, the valves 5 and 6 were opened, and the pressure was reduced to normal pressure with the vacuum pump 9 over 2 hours. Furthermore, the carrier treatment tank was heat-treated at 160 ° C. for 2 hours to produce a carrier.

(Developer)
The developer of the present invention is a two-component developer containing the carrier of the present invention and a toner.
The mixing ratio of the toner and the carrier in the developer is preferably 1 to 10.0 parts by mass of the toner with respect to 100 parts by mass of the carrier.

  The toner includes at least a binder resin and a colorant, and may include a release agent, a charge control agent, and other components as necessary.

<Toner>
The method for producing the toner is not particularly limited and may be appropriately selected depending on the intended purpose. It is a pulverization method, a suspension in which an oil phase is emulsified, suspended or aggregated in an aqueous medium to form toner base particles. There are a polymerization method, an emulsion polymerization method, a polymer suspension method, and the like. Among these, the polymer suspension method is particularly preferable.

-Binder resin-
The binder resin is not particularly limited and may be appropriately selected from known ones according to the purpose. For example, a homopolymer of styrene such as polystyrene, poly-p-styrene, polyvinyltoluene, or a substituted product thereof. Styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-methacrylic acid copolymer Polymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer Polymer, styrene-vinyl methyl ether copolymer, styrene-vinyl methyl ketone Copolymer, styrene-butadiene copolymer, styrene-isopropyl copolymer, styrene-copolymer such as styrene-maleic ester copolymer, polythyme methacrylate resin, polybutyl methacrylate resin, polyvinyl chloride resin , Polyvinyl acetate resin, polyethylene resin, polyester resin, polyurethane resin, epoxy resin, polyvinyl butyral resin, polyacrylic acid resin, rosin resin, modified rosin resin, terpene resin, phenol resin, aliphatic or aromatic hydrocarbon resin, aromatic Family petroleum resin. These may be used alone or in combination of two or more.

-Colorant-
The colorant is not particularly limited and may be appropriately selected from known dyes and pigments according to the purpose. For example, carbon black, nigrosine dye, iron black, naphthol yellow S, Hansa yellow (10G, 5G, G), Cadmium yellow, Yellow iron oxide, Ocher, Yellow lead, Titanium yellow, Polyazo yellow, Oil yellow, Hansa yellow (GR, A, RN, R), Pigment yellow L, Benzidine yellow (G, GR) , Permanent Yellow (NCG), Vulcan Fast Yellow (5G, R), Tartrazine Lake, Quinoline Yellow Lake, Anthrazan Yellow BGL, Isoindolinone Yellow, Bengala, Red Tan, Lead Zhu, Cadmium Red, Cadmium Mercury Red, Antimony Zhu, Permanent Red 4R, Parallel , Faise red, parachlor ortho nitroaniline red, Resol Fast Scarlet G, Brilliant Fast Scarlet, Brilliant Carmine BS, Permanent Red (F2R, F4R, FRL, FRLL, F4RH), Fast Scarlet VD, Belkan Fast Rubin B, Brilliant Scarlet G, Risor Rubin GX, Permanent Red F5R, Brilliant Carmine 6B, Pigment Scarlet 3B, Bordeaux 5B, Toluidine Maroon, Permanent Bordeaux F2K, Helio Bordeaux BL, Bordeaux 10B, Bon Maroon Light, Bon Maroon Medium, Eosin Lake, Rhodamine Lake B, rhodamine lake Y, alizarin lake, thioindigo red B, thioindigo maroon, oil le Quinacridone red, pyrazolone red, polyazo red, chrome vermilion, benzidine orange, perinone orange, oil orange, cobalt blue, cerulean blue, alkaline blue rake, peacock blue rake, Victoria blue rake, metal-free phthalocyanine blue, phthalocyanine blue, Fast Sky Blue, Indanthrene Blue (RS, BC), Indigo, Ultramarine Blue, Bitumen, Anthraquinone Blue, Fast Violet B, Methyl Violet Lake, Cobalt Purple, Manganese Purple, Dioxane Violet, Anthraquinone Violet, Chrome Green, Zinc Green, Oxidation Chrome, Pyridian, Emerald Green, Pigment Green B, Naphthol Green B, Green Gold, Acid Guri Enlake, malachite green lake, phthalocyanine green, anthraquinone green, titanium oxide, zinc white, lithopone, and the like. These may be used individually by 1 type and may use 2 or more types together.

  The content of the colorant in the toner is preferably 1 to 15% by mass, and more preferably 3 to 10% by mass.

  The colorant may be used as a master batch combined with a resin. The resin is not particularly limited and may be appropriately selected from known ones according to the purpose. For example, styrene or a substituted polymer thereof, styrene copolymer, polymethyl methacrylate resin, polybutyl Methacrylate resin, polyvinyl chloride resin, polyvinyl acetate resin, polyethylene resin, polypropylene resin, polyester resin, epoxy resin, epoxy polyol resin, polyurethane, polyamide, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, fat Aromatic hydrocarbon resin, alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, paraffin and the like. These may be used individually by 1 type and may use 2 or more types together.

-Release agent-
There is no restriction | limiting in particular as said mold release agent, According to the objective, it can select suitably from well-known things, For example, waxes etc. are mentioned suitably.

  Examples of the waxes include carbonyl group-containing waxes, polyolefin waxes, long chain hydrocarbons, and the like. These may be used individually by 1 type and may use 2 or more types together. Among these, a carbonyl group-containing wax is preferable.

  Examples of the carbonyl group-containing wax include polyalkanoic acid esters, polyalkanol esters, polyalkanoic acid amides, polyalkylamides, dialkyl ketones, and the like. Examples of the polyalkanoic acid ester include carnauba wax, montan wax, trimethylolpropane tribehenate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, and 1,18-octadecane. Examples thereof include diol distearate. Examples of the polyalkanol ester include tristearyl trimellitic acid and distearyl maleate. Examples of the polyalkanoic acid amide include dibehenyl amide. Examples of the polyalkylamide include trimellitic acid tristearylamide. Examples of the dialkyl ketone include distearyl ketone. Of these carbonyl group-containing waxes, polyalkanoic acid esters are particularly preferred.

  Examples of the polyolefin wax include polyethylene wax and polypropylene wax.

  Examples of the long chain hydrocarbon include paraffin wax and sazol wax.

  There is no restriction | limiting in particular as melting | fusing point of the said mold release agent, Although it can select suitably according to the objective, 40-160 degreeC is preferable, 50-120 degreeC is more preferable, 60-90 degreeC is especially preferable.

  If the melting point is less than 40 ° C., the wax may adversely affect the heat-resistant storage stability, and if it exceeds 160 ° C., cold offset may easily occur during fixing at a low temperature.

  The melt viscosity of the release agent is preferably 5 to 1000 cps, more preferably 10 to 100 cps, as a measured value at a temperature 20 ° C. higher than the melting point of the wax.

  If the melt viscosity is less than 5 cps, the releasability may be lowered, and if it exceeds 1000 cps, the effect of improving hot offset resistance and low-temperature fixability may not be obtained.

  There is no restriction | limiting in particular as content in the said toner of the said mold release agent, Although it can select suitably according to the objective, 1-40 mass% is preferable and 3-30 mass% is more preferable.

  When the content exceeds 40% by mass, the fluidity of the toner may be deteriorated.

-Charge control agent-
The charge control agent is not particularly limited, and a positive or negative charge control agent can be appropriately selected and used depending on whether the charge charged on the photoconductor is positive or negative.

  As the negative charge control agent, for example, a resin or compound having an electron donating functional group, an azo dye, a metal complex of an organic acid, or the like can be used. Specifically, Bontron (product numbers: S-31, S-32, S-34, S-36, S-37, S-39, S-40, S-44, E-81, E-82, E -84, E-86, E-88, A, 1-A, 2-A, 3-A) (above, manufactured by Orient Chemical Industry Co., Ltd.), Kaya Charge (part numbers: N-1, N-2), Kaya Set black (product number: T-2, 004) (above, Nippon Kayaku Co., Ltd.), Eisenspiron black (T-37, T-77, T-95, TRH, TNS-2) (above, Hodogaya Chemical Kogyo Co., Ltd.), FCA-1001-N, FCA-1001-NB, FCA-1001-NZ, and the like (manufactured by Fujikura Kasei Co., Ltd.).

  As the positive charge control agent, for example, a basic compound such as a nigrosine dye, a cationic compound such as a quaternary ammonium salt, a metal salt of a higher fatty acid, or the like can be used. Specifically, Bontron (part numbers: N-01, N-02, N-03, N-04, N-05, N-07, N-09, N-10, N-11, N-13, P -51, P-52, AFP-B) (above, manufactured by Orient Chemical Co., Ltd.), TP-302, TP-415, TP-4040 (above, manufactured by Hodogaya Chemical Co., Ltd.), Copy Blue PR, Copy Charge ( Product number: PX-VP-435, NX-VP-434) (manufactured by Hoechst), FCA (product number: 201, 201-B-1, 201-B-2, 201-B-3, 201-PB, 201-PZ, 301) (above, manufactured by Fujikura Kasei Co., Ltd.), PLZ (product numbers: 1001, 2001, 6001, 7001) (above, manufactured by Shikoku Kasei Kogyo Co., Ltd.), and the like.

  These may be used individually by 1 type and may use 2 or more types together.

  The addition amount of the charge control agent is determined by the toner production method including the type of the binder resin and the dispersion method, and is not limited to a specific one. 0.1-10 mass parts is preferable with respect to 0.2-5 mass parts. When the addition amount exceeds 10 parts by mass, the chargeability of the toner is too large, the effect of the charge control agent is reduced, the electrostatic attraction with the developing roller is increased, the developer fluidity is reduced, and the image density is increased. If the amount is less than 0.1 parts by mass, the charge rise and charge amount are insufficient, and the toner image may be easily affected.

  In addition to the binder resin, the release agent, the colorant, and the charge control agent, the toner material includes inorganic fine particles, a fluidity improver, a cleaning property improver, a magnetic material, a metal soap, and the like as necessary. Can be added.

  Examples of the inorganic fine particles include silica, titania, alumina, cerium oxide, strontium titanate, calcium carbonate, magnesium carbonate, calcium phosphate, etc., and silica hydrophobized with silicone oil, hexamethyldisilazane, or the like. It is more preferable to use fine particles or titanium oxide subjected to a specific surface treatment.

  Examples of the silica fine particles include, for example, Aerosil (product numbers: 130, 200 V, 200 CF, 300, 300 CF, 380, OX50, TT600, MOX80, MOX170, COK84, RX200, RY200, R972, R974, R976, R805, R811, R812, T805, R202, VT222, RX170, RXC, RA200, RA200H, RA200HS, RM50, RY200, REA200 (above, manufactured by Nippon Aerosil Co., Ltd.), HDK (part number: H20, H2000, H3004, H2000 / 4, H2050EP, H2015EP, H3050EP) , KHD50), HVK2150 (above, manufactured by Wacker Chemical Co., Ltd.), Cabozil (Part No .: L-90, LM-130, LM-150, M-5, PTG, MS-55, -5, HS-5, EH-5, LM-150D, M-7D, MS-75D, TS-720, TS-610, TS-530) (or, can be used Cabot Corp.).

  The addition amount of the inorganic fine particles is preferably 0.1 to 5.0 parts by mass, more preferably 0.8 to 3.2 parts by mass with respect to 100 parts by mass of the toner base particles.

  The method for producing the toner is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include a pulverization method, a monomer composition containing a specific crystalline polymer and a polymerizable monomer. Direct polymerization of the product in the aqueous phase (suspension polymerization method, emulsion polymerization method), specific crystalline polymer, composition containing isocyanate group-containing prepolymer directly in the aqueous phase with amines And a polyaddition reaction method using an isocyanate group-containing prepolymer, a method of dissolving with a solvent, removing the solvent and pulverizing, a melt spraying method, and the like.

  The pulverization method is, for example, a method of obtaining the toner base particles by melting or kneading the toner material, pulverizing, classifying or the like. In the case of the pulverization method, for the purpose of increasing the average circularity of the toner, the shape may be controlled by applying a mechanical impact force to the obtained toner base particles. In this case, the mechanical impact force can be applied to the toner base particles using a device such as a hybridizer or mechanofusion.

  The above toner materials are mixed, and the mixture is charged into a melt kneader and melt kneaded. As the melt kneader, for example, a uniaxial continuous kneader, a biaxial continuous kneader, or a batch kneader using a roll mill can be used. For example, KTK type twin screw extruder manufactured by Kobe Steel, TEM type extruder manufactured by Toshiba Machine Co., Ltd., twin screw extruder manufactured by Casey Kay, PCM type twin screw extruder manufactured by Ikegai Iron Works Co., Ltd. Preferably used. This melt-kneading is preferably performed under appropriate conditions so as not to cause the molecular chains of the binder resin to be broken. Specifically, the melt kneading temperature is performed with reference to the softening point of the binder resin. If the temperature is higher than the softening point, cutting is severe, and if the temperature is too low, dispersion may not proceed.

  In the pulverization, the kneaded product obtained by the kneading is pulverized. In this pulverization, it is preferable that the kneaded material is first coarsely pulverized and then finely pulverized. At this time, a method of pulverizing by colliding with a collision plate in a jet stream, pulverizing particles by colliding with each other in a jet stream, or pulverizing with a narrow gap between a mechanically rotating rotor and a stator is preferably used.

  In the classification, the pulverized product obtained by the pulverization is classified and adjusted to particles having a predetermined particle diameter. Classification can be performed, for example, by removing fine particle portions by a cyclone, a decanter, centrifugation, or the like.

  After the pulverization and classification are completed, the pulverized product is classified into an air stream by centrifugal force or the like to produce a toner having a predetermined particle size.

  The suspension polymerization method is an oil-soluble polymerization initiator, emulsification described later in an aqueous medium in which a colorant, a release agent, and the like are dispersed in a polymerizable monomer and a surfactant and other solid dispersant are contained. Emulsified and dispersed by the method. Thereafter, a polymerization reaction is performed to form particles, and then wet processing for attaching inorganic fine particles to the toner particle surfaces in the present invention may be performed. At that time, it is preferable to treat the toner particles from which excess surfactant and the like are removed by washing.

  Examples of the polymerizable monomer include acrylic acids, methacrylic acid, α-cyanoacrylic acid, α-cyanomethacrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic acid, maleic anhydride, and other acids, acrylamide, By using a part of acrylate or methacrylate having amino group such as methacrylamide, diacetone acrylamide or their methylol compounds, vinyl pyridine, vinyl pyrrolidone, vinyl imidazole, ethyleneimine, dimethylaminoethyl methacrylate, etc. Functional groups can be introduced.

  Further, by selecting a dispersant having an acid group or a basic group as the dispersant to be used, the dispersant can be adsorbed and left on the particle surface to introduce a functional group.

  As the emulsion polymerization method, a water-soluble polymerization initiator and a polymerizable monomer are emulsified in water using a surfactant, and a latex is synthesized by a usual emulsion polymerization method. Separately, a dispersion in which a colorant, a release agent and the like are dispersed in an aqueous medium is prepared, and after mixing, the toner is aggregated to a toner size and heat-fused to obtain a toner. Thereafter, wet processing of inorganic fine particles described later may be performed. A functional group can be introduced on the surface of the toner particles by using a latex similar to the monomer that can be used in the suspension polymerization method.

  Among these, since the selectivity of the resin is high, the low-temperature fixability is high, the granulation property is excellent, and the particle size, particle size distribution, and shape can be easily controlled. And a polymer capable of reacting with the active hydrogen group-containing compound is dissolved or dispersed in an organic solvent to prepare a toner solution, and then the toner solution is emulsified or dispersed in an aqueous medium. In the aqueous medium, the active hydrogen group-containing compound and a polymer capable of reacting with the active hydrogen group-containing compound are reacted to form an adhesive substrate in the form of particles, and the organic solvent is What is obtained by removing is suitable.

  Examples of the toner material include an adhesive base obtained by reacting an active hydrogen group-containing compound, a polymer capable of reacting with the active hydrogen group-containing compound, a binder resin, a charge control agent, and a colorant. And, if necessary, other components such as resin fine particles and a release agent.

  Further, in order to improve the fluidity, storage stability, developability and transferability of the toner, inorganic fine particles such as hydrophobic silica fine powder may be further added to and mixed with the toner base particles produced as described above. For mixing the additives, a general powder mixer is used, but it is preferable to equip a jacket or the like to adjust the internal temperature. In order to change the load history applied to the additive, the additive may be added midway or gradually. In this case, you may change the rotation speed, rolling speed, time, temperature, etc. of a mixer. Also, a strong load may be given first, then a relatively weak load, or vice versa. Examples of the mixing equipment that can be used include a V-type mixer, a rocking mixer, a Ladige mixer, a Nauter mixer, and a Henschel mixer. Next, the toner is obtained by passing through a sieve of 250 mesh or more to remove coarse particles and aggregated particles.

  The shape, size, etc. of the toner are not particularly limited and can be appropriately selected according to the purpose. The average circularity, volume average particle size, volume average particle size and number are as follows. It is preferable to have a ratio to the average particle size (volume average particle size / number average particle size).

  The average circularity is a value obtained by dividing the perimeter of an equivalent circle having the same projected shape as the toner shape by the perimeter of the actual particles, and is preferably 0.900 to 0.980, for example, 0.950 to 0 .975 is more preferred. Note that particles having an average circularity of less than 0.94 are preferably 15% or less.

  If the average circularity is less than 0.900, satisfactory transferability and a high-quality image free from dust may not be obtained. If the average circularity exceeds 0.980, image formation employing blade cleaning or the like is employed. In the system, defective cleaning occurs on the photoconductor and the transfer belt, and in the case of image formation with a high image area ratio such as a photographic image, an untransferred image is formed due to defective paper feeding, etc. The accumulated toner may become a transfer residual toner on the photoconductor, resulting in background smearing of the image, or it may contaminate the charging roller for charging the photoconductor in contact with the original charging ability. It may become impossible to demonstrate.

  The average circularity is measured using a flow particle image analyzer (“FPIA-2100”, manufactured by Sysmex Corporation), and analyzed using analysis software (FPIA-2100 Data Processing Program for FPIA version 00-10). It was. Specifically, 0.1 to 0.5 ml of 10 wt% surfactant (alkylbenzene sulfonate Neogen SC-A, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) is added to a glass 100 ml beaker, and each toner 0.1 ˜0.5 g was added and stirred with a micropartel, and then 80 mL of ion-exchanged water was added. The obtained dispersion was subjected to a dispersion treatment for 3 minutes with an ultrasonic disperser (manufactured by Honda Electronics Co., Ltd.). The shape and distribution of the toner were measured using the FPIA-2100 until the concentration of 5000 to 15000 / μL was obtained. In this measurement method, it is important that the concentration of the dispersion is 5000 to 15000 / μL from the viewpoint of measurement reproducibility of the average circularity. In order to obtain the concentration of the dispersion, it is necessary to change the conditions of the dispersion, that is, the amount of surfactant to be added and the amount of toner. The amount of the surfactant varies depending on the hydrophobicity of the toner as in the measurement of the toner particle diameter described above. If it is added in a large amount, noise due to bubbles is generated, and if it is too small, the toner cannot be sufficiently wetted. It will be enough. Further, the amount of toner added varies depending on the particle size, and it is small for small particle sizes, and needs to be increased for large particle sizes. By adding 5 g, the dispersion concentration can be adjusted to 5000 to 15000 / μl.

  The volume average particle diameter of the toner is not particularly limited and may be appropriately selected depending on the intended purpose. For example, it is preferably 3 to 10 μm, and more preferably 3 to 8 μm.

  When the volume average particle size is less than 3 μm, in the case of a two-component developer, the toner may be fused to the surface of the carrier during a long period of stirring in the developing device, and the charging ability of the carrier may be reduced. Therefore, it becomes difficult to obtain a high-resolution and high-quality image, and when the balance of the toner in the developer is performed, the fluctuation of the toner particle diameter may increase.

  The ratio of the volume average particle diameter to the number average particle diameter (volume average particle diameter / number average particle diameter) in the toner is preferably 1.00 to 1.25, more preferably 1.10 to 1.25.

  The volume average particle diameter and the ratio between the volume average particle diameter and the number average particle diameter (volume average particle diameter / number average particle diameter) are measured using a particle size measuring device (“Multisizer III” manufactured by Beckman Coulter, Inc.). Then, measurement was performed with an aperture diameter of 100 μm, and analysis was performed with analysis software (Beckman Coulter Multisizer 3 Version 3.51). Specifically, 0.5 ml of 10% by weight surfactant (alkylbenzene sulfonate Neogen SC-A, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) is added to a glass 100 ml beaker, and 0.5 g of each toner is added to make microscopic. The mixture was stirred with a spatula, and then 80 ml of ion exchange water was added. The obtained dispersion was subjected to a dispersion treatment for 10 minutes with an ultrasonic disperser (W-113MK-II, manufactured by Honda Electronics Co., Ltd.). The dispersion was measured using the Multisizer III and Isoton III (manufactured by Beckman Coulter, Inc.) as the measurement solution. In the measurement, the toner sample dispersion was dropped so that the concentration indicated by the apparatus was 8 ± 2%. In this measurement method, it is important that the concentration is 8 ± 2% from the viewpoint of the reproducibility of the particle size. Within this concentration range, no error occurs in the particle size.

  The coloration of the toner is not particularly limited and may be appropriately selected according to the purpose, and may be at least one selected from black toner, cyan toner, magenta toner, and yellow toner. Can be obtained by appropriately selecting the type of the colorant, and is preferably a color toner.

<Container with developer>
The container for containing the developer of the present invention is not particularly limited and can be appropriately selected from known ones. For example, a container having a developer container body and a cap is suitable. It is mentioned in.

  The size, shape, structure, material and the like of the developer container body are not particularly limited and can be appropriately selected according to the purpose. For example, the shape is preferably cylindrical. A spiral irregularity is formed on the peripheral surface, and the toner as the contents can be transferred to the discharge port side by rotating, and part or all of the spiral part has a bellows function, etc. Is particularly preferred.

  The material of the developer container main body is not particularly limited, and those having good dimensional accuracy are preferable. For example, a resin is preferable, and among them, for example, polyester resin, polyethylene resin, polypropylene resin, polystyrene resin, Preferable examples include vinyl chloride resin, polyacrylic acid, polycarbonate resin BS resin, and polyacetal resin.

  Such a developer-containing container is easy to store and transport, has excellent handleability, and can be suitably used for replenishing a developer by being detachably attached to a process cartridge, an image forming apparatus, and the like described later.

(Image forming method)
The image forming method of the present invention includes at least an electrostatic latent image forming step, a developing step, a transfer step, and a fixing step, and other steps appropriately selected as necessary, for example, a static elimination step, a cleaning step. , Including recycling process, control process, etc. In the developing step, the developer according to the present invention is used.

  An image forming apparatus for performing the image forming method includes at least an electrostatic latent image carrier, an electrostatic latent image forming unit, a developing unit, a transfer unit, and a fixing unit, and further if necessary. And other means suitably selected, for example, static elimination means, cleaning means, recycling means, control means and the like. The developing means is provided with the developer according to the present invention.

  The electrostatic latent image forming step is a step of forming an electrostatic latent image on the electrostatic latent image carrier.

  The electrostatic latent image carrier (sometimes referred to as “electrophotographic photosensitive member” or “photosensitive member”) is not particularly limited in terms of material, shape, structure, size, etc. Although it can be selected as appropriate, the shape thereof is preferably a drum shape, and examples of the material thereof include inorganic photoreceptors such as amorphous silicon and selenium, organic photoreceptors (OPC) such as polysilane and phthalopolymethine, and the like. Is mentioned. Among these, amorphous silicon or the like is preferable in terms of long life.

  The formation of the electrostatic latent image can be performed, for example, by uniformly charging the surface of the electrostatic latent image carrier and then performing imagewise exposure, and is performed by the electrostatic latent image forming unit. be able to.

  The electrostatic latent image forming means includes, for example, at least a charger that uniformly charges the surface of the electrostatic latent image carrier and an exposure device that exposes the surface of the electrostatic latent image carrier imagewise. Prepare.

  The charging can be performed, for example, by applying a voltage to the surface of the electrostatic latent image carrier using the charger.

  The charger is not particularly limited and may be appropriately selected depending on the purpose. For example, a known contact charging device including a conductive or semiconductive roll, brush, film, rubber blade, etc. And non-contact chargers using corona discharge such as corotrons and corotrons.

  Further, the charger is preferably one that is arranged in contact or non-contact with the electrostatic latent image carrier and charges the surface of the electrostatic latent image carrier by applying DC and AC voltages in a superimposed manner.

  Further, the charger is a charging roller disposed in a non-contact proximity to the electrostatic latent image carrier via a gap tape, and the electrostatic latent image is carried by applying a direct current and an alternating voltage to the charging roller. Those that charge the body surface are preferred.

  The exposure can be performed, for example, by exposing the surface of the latent electrostatic image bearing member imagewise using the exposure device.

  The exposure device is not particularly limited as long as it can expose the surface of the electrostatic latent image carrier charged by the charger so as to form an image to be formed, and is appropriately selected according to the purpose. For example, various exposure devices such as a copying optical system, a rod lens array system, a laser optical system, and a liquid crystal shutter optical system can be used.

  In addition, you may employ | adopt the light back system which performs imagewise exposure from the back surface side of the said electrostatic latent image carrier.

-Development process and development means-
The developing step is a step of developing the electrostatic latent image using the developer of the present invention to form a visible image.

  The visible image is formed by the developing means, and the electrostatic latent image is developed using the developer of the present invention.

  The developing means is not particularly limited as long as it can be developed using the developer of the present invention, and can be appropriately selected from known ones. For example, the developer of the present invention is contained, and the static Those having at least a developing device capable of bringing the developer into contact or non-contact with the electrostatic latent image are preferable, and a developing device including the developer-containing container is more preferable.

  The developing unit may be a dry developing type, a wet developing type, a single color developing unit, or a multi-color developing unit. For example, a developer having a stirrer for charging the developer by frictional stirring and a rotatable magnet roller is preferable.

  In the developing device, for example, the toner and the carrier are mixed and agitated, and the toner is charged by friction at that time, and held on the surface of the rotating magnet roller in a raised state to form a magnetic brush. . Since the magnet roller is disposed in the vicinity of the electrostatic latent image carrier (photoconductor), a part of the toner constituting the magnetic brush formed on the surface of the magnet roller is electrically attracted. It moves to the surface of the electrostatic latent image carrier (photoconductor) by force. As a result, the electrostatic latent image is developed with the toner, and a visible image is formed with the toner on the surface of the electrostatic latent image carrier (photoconductor).

-Transfer process and transfer means-
The transfer step is a step of transferring the visible image onto a recording medium. After the primary transfer of the visible image onto the intermediate transfer member using an intermediate transfer member, the visible image is transferred onto the recording medium. A primary transfer step of forming a composite transfer image by transferring a visible image onto an intermediate transfer body using two or more colors, preferably full color toner as the toner, and a composite transfer image; A mode including a secondary transfer step of transferring the transfer image onto the recording medium is more preferable.

  The transfer can be performed, for example, by charging the latent electrostatic image bearing member (photoconductor) of the visible image using a transfer charger, and can be performed by the transfer unit. The transfer means includes a primary transfer means for transferring a visible image onto an intermediate transfer member to form a composite transfer image, and a secondary transfer means for transferring the composite transfer image onto a recording medium. Embodiments are preferred.

  The intermediate transfer member is not particularly limited and may be appropriately selected from known transfer members according to the purpose. For example, a transfer belt and the like are preferable.

  The transfer means (the primary transfer means and the secondary transfer means) is a transfer for peeling and charging the visible image formed on the electrostatic latent image carrier (photoconductor) to the recording medium side. It is preferable to have at least a vessel. There may be one transfer means or two or more transfer means.

  Examples of the transfer device include a corona transfer device using corona discharge, a transfer belt, a transfer roller, a pressure transfer roller, and an adhesive transfer device.

  The recording medium is not particularly limited and can be appropriately selected from known recording media (recording paper).

  The fixing step is a step of fixing the visible image transferred to the recording medium using a fixing device, and may be performed each time the developer of each color is transferred to the recording medium, or the developer of each color. On the other hand, it may be carried out at the same time in a state where these are laminated.

  There is no restriction | limiting in particular as said fixing device, Although it can select suitably according to the objective, A well-known heating-pressing means is suitable. Examples of the heating and pressing means include a combination of a heating roller and a pressure roller, a combination of a heating roller, a pressure roller, and an endless belt.

  The fixing device includes a heating body including a heating element, a film in contact with the heating body, and a pressure member in pressure contact with the heating body through the film, and the film and the pressure member It is preferably a unit that heats and fixes a recording medium on which an unfixed image is formed.

  The heating in the heating and pressing means is usually preferably 80 to 200 ° C.

  In the present invention, for example, a known optical fixing device may be used together with or in place of the fixing step and the fixing unit depending on the purpose.

  The neutralization step is a step of performing neutralization by applying a neutralization bias to the electrostatic latent image carrier, and can be suitably performed by a neutralization unit.

  The neutralization means is not particularly limited, and may be appropriately selected from known neutralizers as long as it can apply a neutralization bias to the electrostatic latent image carrier. Preferably mentioned.

  The cleaning step is a step of removing the toner remaining on the electrostatic latent image carrier and can be suitably performed by a cleaning unit.

  The cleaning unit is not particularly limited, and may be selected from known cleaners as long as it can remove the toner remaining on the electrostatic latent image carrier. For example, a magnetic brush cleaner Suitable examples include electrostatic brush cleaners, magnetic roller cleaners, blade cleaners, brush cleaners, web cleaners, and the like.

  The recycling step is a step of recycling the toner removed by the cleaning step to the developing unit, and can be suitably performed by the recycling unit.

  There is no restriction | limiting in particular as said recycling means, A well-known conveyance means etc. are mentioned.

  The control means controls the steps, and each step can be suitably performed by the control means.

  The control means is not particularly limited as long as the movement of each means can be controlled, and can be appropriately selected according to the purpose. Examples thereof include devices such as a sequencer and a computer.

  One aspect of the image forming method of the present invention will be described. An image forming apparatus 100 shown in FIG. 2 includes a photosensitive drum 10 as the electrostatic latent image carrier (hereinafter referred to as “photosensitive member 10”), a charging roller 20 as the charging unit, and exposure as the exposure unit. The apparatus 30 includes a developing device 40 as the developing means, an intermediate transfer member 50, a cleaning device 60 as the cleaning means having a cleaning blade, and a static elimination lamp 70 as the static elimination means.

  The intermediate transfer member 50 is an endless belt, and is designed to be movable in the direction of an arrow by three rollers 51 that are arranged inside and stretched. Part of the three rollers 51 also functions as a transfer bias roller that can apply a predetermined transfer bias (primary transfer bias) to the intermediate transfer member 50. The intermediate transfer body 50 is provided with a cleaning device 90 having a cleaning blade in the vicinity thereof, and for transferring (secondary transfer) a developed image (toner image) to a transfer sheet 95 as a final transfer material. A transfer roller 80 serving as a transfer unit to which a transfer bias can be applied is disposed to face the transfer roller 80. Around the intermediate transfer member 50, a corona charger 58 for applying a charge to the toner image on the intermediate transfer member 50 is arranged between the photosensitive member 10 and the intermediate transfer member 50 in the rotation direction of the intermediate transfer member 50. It is disposed between the contact portion and the contact portion between the intermediate transfer member 50 and the transfer paper 95.

  The developing device 40 includes a developing belt 41 as the developer carrying member, and a black developing unit 45K, a yellow developing unit 45Y, a magenta developing unit 45M, and a cyan developing unit 45C provided around the developing belt 41. . The black developing unit 45K includes a developer accommodating portion 42K, a developer supplying roller 43K, and a developing roller 44K. The yellow developing unit 45Y includes a developer accommodating portion 42Y, a developer supplying roller 43Y, and a developing roller 44Y. The magenta developing unit 45M includes a developer accommodating portion 42M, a developer supplying roller 43M, and a developing roller 44M, and the cyan developing unit 45C includes a developer accommodating portion 42C and a developer supplying roller 43C. And a developing roller 44C. The developing belt 41 is an endless belt, is rotatably stretched around a plurality of belt rollers, and a part thereof is in contact with the photoconductor 10.

  In the image forming apparatus 100 shown in FIG. 2, for example, the charging roller 20 charges the photosensitive drum 10 uniformly. The exposure device 30 performs imagewise exposure on the photosensitive drum 10 to form an electrostatic latent image. The electrostatic latent image formed on the photosensitive drum 10 is developed by supplying toner from the developing device 40 to form a visible image (toner image). The visible image (toner image) is transferred (primary transfer) onto the intermediate transfer member 50 by the voltage applied from the roller 51, and further transferred (secondary transfer) onto the transfer paper 95. As a result, a transfer image is formed on the transfer paper 95. The residual toner on the photoconductor 10 is removed by the cleaning device 60, and the charge on the photoconductor 10 is temporarily removed by the charge eliminating lamp 70.

  As still another embodiment of the image forming method of the present invention, an image forming apparatus shown in FIG. 3 will be described. The image forming apparatus 100 shown in FIG. 3 does not include the developing belt 41 in the image forming apparatus 100 shown in FIG. 2, and a black developing unit 45K, a yellow developing unit 45Y, a magenta developing unit 45M, and Except for the fact that the cyan developing unit 45C is arranged directly opposite, it has the same configuration as the image forming apparatus 100 shown in FIG.

  According to the image forming method of the present invention, since the developer of the present invention is used in the developing step, a high quality image can be efficiently formed.

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

(Production Example 1)
-Production of Toner 1-
It is represented by 100 parts by mass of a polyester resin (weight average molecular weight = 12,000), 2 parts by mass of a copper phthalocyanine pigment, and the following structural formula (A) (nonylene perfluoroether, iodine salt of p-trimethylaminopropylamidophenyl). 2 parts by weight of the charge control agent is kneaded at 120 ° C. using a hot roll, cooled and solidified, pulverized and classified, and the volume average particle diameter is 7.1 μm, the number average particle diameter is 5.8 μm, Toner base particles having an average circularity of 0.953 were obtained.

  Next, 0.5 parts by mass of silica R972 (manufactured by Nippon Aerosil Co., Ltd.) was added to and mixed with 100 parts by mass of the obtained toner base particles to prepare “Toner 1”.

(Production Example 2)
-Production of Toner 2-
100 parts by mass of a polyester resin (weight average molecular weight = 12,000), 5 parts by mass of carbon black, and 2 parts by mass of a chromium-containing azo dye represented by the following structural formula (B) were kneaded at 120 ° C. using a hot roll. After cooling and solidifying, the mixture was pulverized and classified to obtain toner base particles having a volume average particle size of 7.3 μm, a number average particle size of 6.0 μm, and an average circularity of 0.955.

  Next, 0.5 parts by mass of silica R972 (manufactured by Nippon Aerosil Co., Ltd.) was added to 100 parts by mass of the obtained toner base particles and mixed to prepare “Toner 2”.

(Production Example 3)
<Preparation of Toner 3>
-Synthesis of organic fine particle emulsion-
In a reaction vessel equipped with a stir bar and a thermometer, 683 parts by mass of water, 11 parts by mass of sodium salt of ethylene oxide methacrylate adduct sulfate (Eleminol RS-30, manufactured by Sanyo Chemical Industries, Ltd.), 83 parts by mass of styrene Part, 83 parts by weight of methacrylic acid, 110 parts by weight of butyl acrylate, and 1 part by weight of ammonium persulfate were added and stirred at 400 rpm for 15 minutes to obtain a white emulsion. This emulsion was heated to raise the system temperature to 75 ° C. and reacted for 5 hours. Next, 30 parts by mass of a 1% by mass ammonium persulfate aqueous solution was added, and the mixture was aged at 75 ° C. for 5 hours to form a vinyl resin (a copolymer of methacrylic acid-butyl acrylate-methacrylic acid ethylene oxide adduct sulfate sodium salt). An aqueous dispersion was obtained. This is designated as [fine particle dispersion 1].
The volume average particle diameter of the fine particles contained in the obtained [fine particle dispersion 1] was measured with a particle size distribution measuring apparatus (“LA-920”, manufactured by Horiba, Ltd.) using a laser scattering method, and found to be 105 nm. It was. In addition, a part of [Fine Particle Dispersion 1] was dried to isolate only the resin component. The glass transition temperature (Tg) of this resin was 59 ° C., and the weight average molecular weight (Mw) was 150,000.

-Preparation of aqueous phase-
990 parts by mass of water, 83 parts by mass of [Fine Particle Dispersion 1], 37 parts by mass of a 48.5% aqueous solution of dodecyl diphenyl ether disulfonate (Eleminol MON-7, manufactured by Sanyo Chemical Industries Ltd.), and 90 parts by mass of ethyl acetate The mixture was stirred to obtain a milky white liquid. This liquid is designated [Aqueous Phase 1].

-Synthesis of low molecular weight polyester-
In a reaction vessel equipped with a cooling tube, a stirrer, and a nitrogen introduction tube, 229 parts by mass of bisphenol A ethylene oxide 2 mol adduct, 529 parts by mass of bisphenol A propylene oxide 3 mol adduct, 208 parts by mass of terephthalic acid, 46 adipic acid 46 Part by mass and 2 parts by mass of dibutyltin oxide were charged and reacted at 230 ° C. for 8 hours under normal pressure. Subsequently, after reacting under reduced pressure of 10 to 15 mmHg for 5 hours, 44 parts by mass of trimellitic anhydride was put in the reaction vessel and reacted at 180 ° C. and normal pressure for 2 hours to synthesize [low molecular weight polyester 1].
The obtained [low molecular weight polyester 1] had a glass transition temperature (Tg) of 45 ° C., a weight average molecular weight (Mw) of 5800, a number average molecular weight of 2600, and an acid value of 24 mgKOH / g. .

-Synthesis of polyester prepolymer-
In a reaction vessel equipped with a cooling tube, a stirrer, and a nitrogen introduction tube, 682 parts by mass of bisphenol A ethylene oxide 2 mol adduct, 81 parts by mass of bisphenol A propylene oxide 2 mol adduct, 283 parts by mass of terephthalic acid, 22 parts by mass of merit acid and 2 parts by mass of dibutyltin oxide were added and reacted at 230 ° C. for 8 hours under normal pressure. Subsequently, it reacted for 5 hours under the reduced pressure of 10-15 mmHg, and the [intermediate polyester 1] was synthesize | combined.
The obtained [Intermediate polyester 1] had a number average molecular weight of 2,100, a weight average molecular weight of 9,500, a glass transition temperature (Tg) of 55 ° C., an acid value of 0.5 mgKOH / g, and a hydroxyl value of 51.
Next, 410 parts by mass of [Intermediate Polyester 1], 89 parts by mass of isophorone diisocyanate and 500 parts by mass of ethyl acetate are placed in a reaction vessel equipped with a cooling tube, a stirrer, and a nitrogen introduction tube, and are heated at 100 ° C. for 5 hours. Reaction was performed to obtain [Prepolymer 1].
[Prepolymer 1] obtained had a free isocyanate mass% of 1.74%.

-Synthesis of ketimine-
In a reaction vessel equipped with a stir bar and a thermometer, 170 parts by mass of isophoronediamine and 75 parts by mass of methyl ethyl ketone were charged and reacted at 50 ° C. for 5 hours to synthesize [ketimine compound 1]. The amine value of the obtained [ketimine compound 1] was 418.

-Preparation of masterbatch (MB)-
1,200 parts by mass of water, 540 parts by mass of carbon black (PBk-7: Printex 60, manufactured by Degussa) [DBP oil absorption = 114 ml / 100 mg, pH = 10], and polyester resin (manufactured by Sanyo Chemical Industries, RS801) 1,200 parts by mass was added and mixed with a Henschel mixer (Mitsui Mining Co., Ltd.). The obtained mixture was kneaded at 150 ° C. for 30 minutes using two rolls, rolled and cooled, and pulverized with a pulverizer to obtain a master batch. This is designated as [Masterbatch 1].

-Preparation of oil phase-
In a reaction vessel equipped with a stir bar and a thermometer, 300 parts by weight of [low molecular weight polyester 1], 90 parts by weight of carnauba wax, 10 parts by weight of rice wax, and 1000 parts by weight of ethyl acetate were charged and stirred while stirring. After dissolving at 0 ° C., it was rapidly cooled to 4 ° C. at once. Using a bead mill (Ultra Visco Mill, manufactured by Imex Co., Ltd.), the liquid feeding speed is 1 kg / hr, the disk peripheral speed is 6 m / sec, and 0.5 mm zirconia beads are filled by 80% by volume, and dispersion is performed under conditions of 3 passes. And a wax dispersion having a volume average particle size of 0.6 μm was obtained.
Next, 500 parts by mass of [Masterbatch 1] and 640 parts by mass of a 70% ethyl acetate solution of [Low molecular weight polyester 1] were added and mixed for 10 hours. [Oil phase 1] adjusted to mass% was prepared.

-Preparation of polymerized toner-
[Oil Phase 1] 73.2 parts by mass, [Prepolymer 1] 6.8 parts by mass, and [Ketimine Compound 1] 0.48 parts by mass were placed in a container and mixed well with [Emulsified oil phase 1]. Aqueous phase 1] 120 parts by mass was added, mixed with a homomixer for 1 minute, and then agitated with a paddle for 1 hour with gentle agitation to obtain [Emulsion slurry 1].
The obtained [emulsified slurry 1] was desolvated at 30 ° C. for 1 hour, further aged at 60 ° C. for 5 hours, washed with water, filtered and dried, and then sieved with a mesh having a mesh size of 75 μm. Toner base particles having a particle size of 6.1 μm, a number average particle size of 5.4 μm, and an average circularity of 0.972 were prepared.
Next, 0.7 parts by mass of hydrophobic silica and 0.3 parts by mass of hydrophobized titanium oxide were mixed with 100 parts by mass of the obtained toner base particles using a Henschel mixer to prepare “Toner 3”.

Example 1
-Production of carrier 1-
100 parts by mass of ferrite core material having a volume average particle size of 35 μm (saturation magnetic moment at 1 k gauss = 65 emu / g) and alumina (Sumitomo Chemical Co., Ltd., Sumicorundum AA-04, 0.4 μm, axial ratio: 1. 1) 1 part by mass is charged into a high-speed fluid mixer Supermixer SMP-2 (produced by Kawata Co., Ltd., internal volume 1.0 L) and mixed under mixing condition 1 (2500 rpm, mixed for 5 minutes) to obtain a mixture 1 Got.

  Using the apparatus shown in FIG. 1, silicone resin A (weight average molecular weight (Mw) = 12,500, number average molecular weight (Mn) = 6,500, Mw / Mn = in a carrier treatment tank (internal volume 400 mL). 1.92) 7 parts by mass, 1 part of the above-mentioned mixture 1 and 100 parts by mass were added, and the valve 3 was opened while stirring. After supplying to 25 MPa and 40 ° C., the valve 3 was closed.

After maintaining the inside of the carrier treatment tank at 25 MPa and 40 ° C. for 2 hours, the valve 5 and the valve 6 were opened, and the pressure was reduced to normal pressure with the vacuum pump 1 over 2 hours. Further, the carrier treatment tank was heat-treated at 160 ° C. for 2 hours. The coating material that was not used could be recovered from the raw material recovery tank and reused.
The thickness of the coating layer of the obtained carrier 1 was 0.55 μm, and the electric resistance was Log R 13.5 Ω · cm.

(Example 2)
-Production of carrier 2-
In Example 1, silicone resin A was changed to silicone resin B (weight average molecular weight (Mw) = 18,000, number average molecular weight (Mn) = 9,000, Mw / Mn = 2.00, transition temperature from solid = A carrier 2 was produced in the same manner as in Example 1 except that the temperature was changed to 60 ° C.
The thickness of the coating layer of the obtained carrier 2 was 0.52 μm, and the electric resistance was Log R 13.5 Ω · cm.

(Example 3)
-Production of carrier 3-
A carrier 3 was produced in the same manner as in Example 1, except that the mixing condition 1 was changed to the mixing condition 2 (1500 rpm, mixing for 5 minutes).
The thickness of the coating layer of the obtained carrier 3 was 0.54 μm, and the electric resistance was LogR13.7Ω · cm.

Example 4
-Production of carrier 4-
A carrier 4 was produced in the same manner as in Example 2, except that the mixing condition 1 was changed to the mixing condition 2 (1500 rpm, mixing for 5 minutes).
The thickness of the coating layer of the obtained carrier 4 was 0.52 μm, and the electric resistance was Log R 13.8 Ω · cm.

(Example 5)
-Production of carrier 5-
100 parts by mass of ferrite core material having a volume average particle size of 35 μm (saturation magnetic moment at 1 k gauss = 65 emu / g) and alumina (Sumitomo Chemical Co., Ltd., Sumicorundum AA-04, 0.4 μm, axial ratio: 1. 1) After mixing 1 part by mass with a YGG mixer (manufactured by Yayoi Co., Ltd.) for 20 minutes, the hybridizer NHS-1 type (manufactured by Nara Machinery Co., Ltd.) is filled and mixed at a rotational speed of 7000 rpm for 5 minutes. Mixture 2 was obtained.
Using the apparatus shown in FIG. 1, silicone resin A (weight average molecular weight (Mw) = 12,500, number average molecular weight (Mn) = 6,500, Mw / Mn = in a carrier treatment tank (internal volume 400 mL). 1.92) 7 parts by mass, 2 parts of the above-mentioned mixture, and 100 parts by mass were added, the valve 3 was opened while stirring, and carbon dioxide (purity = 99.5%, manufactured by Gastec Service Co., Ltd.) was supplied with the pressure pump 1. After supplying to 25 MPa and 40 ° C., the valve 3 was closed.

After maintaining the inside of the carrier treatment tank at 25 MPa and 40 ° C. for 2 hours, the valve 5 and the valve 6 were opened, and the pressure was reduced to normal pressure with the vacuum pump 1 over 2 hours. Further, the carrier treatment tank was heat-treated at 160 ° C. for 2 hours. The coating material that was not used could be recovered from the raw material recovery tank and reused.
The thickness of the coating layer of the obtained carrier 5 was 0.50 μm, and the electric resistance was LogR13.1 Ω · cm.

(Comparative Example 1)
-Production of comparative carrier 1-
Toluene solution (solid content concentration 10 mass) of silicone resin A (mass average molecular weight = 12,500, number average molecular weight (Mn) = 6,500, Mw / Mn = 1.92, phase transition temperature from solid = 45 ° C.) %) 1000 parts by mass, catalyst [(CH ₃ ) ₂ Sn (OCOCH ₃ ) ₂ ] 5 parts by mass dispersion, and alumina (Sumitomo Chemical Co., Ltd., Sumiko Random AA-04, 0.4 μm, axial ratio 1) .1) After stirring 50 parts by mass, a ferrite core material having a volume average particle diameter of 35 μm (saturated magnetic moment at 1 k gauss = 65 emu / g) is used at a temperature of 100 ° C. using a fluidized bed type coating apparatus. Then, the ferrite particles coated with the silicone resin obtained at a rate of 50 g / min for 20 minutes were heated at 200 ° C. for 1 hour to prepare a comparative carrier 1.
With respect to the obtained comparative carrier 1, the average thickness of the coating layer measured in the same manner as in Example 1 was 0.62 μm, and the electric resistance was LogR14.2 Ω · cm.

(Examples 6 to 12, Comparative Example 2)
-Production of developer-
The produced carriers 1 to 5 and comparative carrier 1 and toners 1 to 3 were combined as shown in Table 1 below, and developers of Examples 6 to 12 and Comparative Example 2 were produced by a conventional method.

  Using the obtained developers, image density, toner scattering property, background stain, and comprehensive evaluation were performed as follows. The results are shown in Table 1.

<Image density>
Next, each developer obtained was attached to copy paper (TYPE6000 <70W>, manufactured by Ricoh Co., Ltd.) using a tandem color image forming apparatus (image Neo 450, manufactured by Ricoh Co., Ltd.). A solid image having an amount of 1.00 ± 0.05 mg / cm ² was formed. The solid image was repeatedly formed on 1 million copy sheets.
The image density of the obtained solid image was visually observed for the initial stage and after the endurance of 1,000,000 sheets, and evaluated based on the following evaluation criteria. Note that the higher the image density obtained, the higher the density image can be formed. This evaluation corresponds to an embodiment of the image forming method of the present invention.
〔Evaluation criteria〕
(Double-circle): The image density did not change and the high image quality was obtained at the initial stage and after the endurance of 1 million sheets.
◯: After 1 million sheets were used, the image density was slightly reduced, but high image quality was obtained.
(Triangle | delta): After 1 million sheet endurance, the image density fell and the image quality fell.
X: After enduring 1 million sheets, the image density was remarkably lowered and the image quality was greatly lowered.

<Toner scattering property>
The following evaluation criteria were used to visually check the degree of toner contamination in the machine when 1 million sheets of a 5% image area ratio chart were continuously output using a tandem color image forming apparatus (Imagio Neo 450, manufactured by Ricoh Co., Ltd.). Based on 4 grades.
〔Evaluation criteria〕
A: There is no toner contamination in the machine and it is in an excellent state.
◯: There is no toner contamination in the machine and it is in a good state.
Δ: There is toner contamination in the machine, but it is a practically usable level.
X: Toner contamination in the machine is severe and the level is not practical.

<Soil dirt>
The following evaluation was made by visually evaluating the degree of background staining on the image background when a chart with an image area ratio of 5% was output continuously for 1 million sheets using a tandem color image forming apparatus (Imagio Neo 450, manufactured by Ricoh Co., Ltd.). Evaluation was made according to the criteria.
〔Evaluation criteria〕
○: No background stains in the image background.
Δ: Soil is slightly generated in the background portion of the image.
X: Soil is generated in the background portion of the image.

<Comprehensive evaluation>
From the above evaluation results, the following evaluation criteria were comprehensively evaluated.
〔Evaluation criteria〕
◎: Very good ○: Good ×: Bad

  From the results of Table 1, the developers of Examples 6 to 12 using the carriers 1 to 5 using the coating material in which the fine particles are dispersed on the surface of the core material and dissolved in the supercritical fluid are developed in Comparative Example 2. Compared to the agent, it was confirmed that there was no toner scattering and no background stain and a high image density was obtained.

It is the schematic which shows an example of the manufacturing apparatus used for the manufacturing method of the carrier of this invention. It is a schematic explanatory drawing of the image forming apparatus which shows one Embodiment of the image forming method of this invention. It is a schematic explanatory drawing of the image forming apparatus which shows one Embodiment of the image forming method of this invention.

Explanation of symbols

10 Photoconductor (Photoconductor drum)
20 charging roller 41 developing belt 45K black developing unit 45Y yellow developing unit 45M magenta developing unit 45C cyan developing unit 50 intermediate transfer member 60 cleaning device

Claims (11)

  A method for producing a carrier for developing an electrostatic latent image, wherein a coating layer is formed on a surface of a core material, the step of mixing the core material and fine particles to form a mixture of the core material and fine particles, and the mixture and the coating And a step of mixing a resin in a supercritical fluid or a subcritical fluid to form a coating layer on the surface of the mixture.   The method for producing a carrier for developing an electrostatic latent image according to claim 1, wherein the fine particles are fixed to the surface of the core material.   The method for producing a carrier for developing an electrostatic latent image according to claim 1, wherein the mixture is formed by a mechanochemical method.   2. The method for producing a carrier for developing an electrostatic latent image according to claim 1, wherein the coating layer is formed by controlling the pressure or temperature of the supercritical fluid or subcritical fluid.   The method for producing a carrier for developing an electrostatic latent image according to claim 1, wherein the supercritical fluid or subcritical fluid is carbon dioxide.   6. The method for producing a carrier for developing an electrostatic latent image according to claim 1, wherein the fine particles are made of a material having a composition different from that of the coating layer.   7. The method for producing a carrier for developing an electrostatic latent image according to claim 1, wherein the fine particles are a metal oxide.   The method for producing a carrier for developing an electrostatic latent image according to any one of claims 1 to 7, wherein the core material has a volume average particle size in a range of 20 to 50 µm.   An electrostatic latent image developing carrier produced by the production method according to claim 1.   A developer comprising the carrier according to claim 9 mixed with a toner.   An electrostatic latent image forming step of forming an electrostatic latent image on the electrostatic latent image carrier, a developing step of developing the electrostatic latent image using a developer to form a visible image, and the visible image An image forming method comprising at least a transfer step of transferring the toner image to a recording medium and a fixing step of fixing the transferred image transferred to the recording medium, wherein the developer is the developer according to claim 10. An image forming method.

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