JP5104345B2 - Electrostatic image developing carrier, electrostatic image developing developer, and image forming apparatus - Google Patents

Description

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

  A method for visualizing image information through an electrostatic latent image (electrostatic image) such as electrophotography is currently used in various fields. In electrophotography, an electrostatic latent image formed on a photoreceptor by charging and exposure processes contains an electrostatic charge image developing toner (hereinafter sometimes referred to simply as “toner”). It is developed with an agent (hereinafter sometimes simply referred to as “developer”), and visualized through a transfer and fixing process. As a developer used for development, a two-component developer including a toner and a carrier for developing an electrostatic image (hereinafter sometimes simply referred to as “carrier”) and a toner used alone such as a magnetic toner are used. There are component developers, but the two-component developer has characteristics such as good controllability because the carrier shares functions such as stirring, transport and charging of the developer and is separated as a developer. Is currently widely used.

  Carriers are generally divided into resin-coated carriers that have a resin coating layer on the surface of the magnetic core material (carrier core material) and uncoated carriers that do not have a coating layer on the surface. Since resin-coated carriers are superior, various types of resin-coated carriers have been developed and put into practical use.

  Image forming apparatuses using electrophotography such as printers and copiers are used for a wide variety of purposes. In such an image forming apparatus, generally, the residual matter such as toner and carrier remaining on the surface of the photoreceptor is removed by a cleaning means such as a cleaning blade. For example, when high-speed printing in black and white is performed and printing at high speed and low speed is repeated alternately, such as when printing at low speed with color printing using OHP or cardboard, the gap between the cleaning blade and the photoconductor Residues accumulated in the tank are likely to accumulate densely. This is because the residues are densely arranged during low-speed printing and are consolidated during high-speed printing. At this time, the consolidated reservoir is difficult to clean. As a result, the carrier contained therein may cause chipping of the cleaning blade or circumferential damage to the photoreceptor, which may appear as streak-like image defects on the image.

  As a method for preventing this, there is a method for reducing the friction of the carrier. For example, a resin-coated carrier using a silicone resin that is a low-friction resin as a coating resin, a modified silicone resin that takes chargeability into account (Patent Documents 1 to 3), and a resin-coated carrier in which a fluorine component is introduced into the resin coating layer (Patent Document 4) proposes a carrier with reduced friction.

  Also, the carrier shape is made spherical, the contact portion with the photoconductor is made smaller, the carrier having improved cleaning properties (Patent Document 5), and the convex and concave portions based on the fine crystal particles of spherical ferrite are exposed. A coated carrier has been proposed (Patent Document 6).

JP 2005-91690 A Japanese Unexamined Patent Publication No. 7-28281 JP-A-10-39549 Japanese Patent Laid-Open No. 11-65176 JP 2000-122347 A JP-A-4-93954

  The present invention relates to a carrier for developing an electrostatic image capable of suppressing generation of streak image defects and obtaining a good image even when low-speed printing and high-speed printing are alternately repeated, and an electrostatic image containing the carrier. A developing developer and an image forming apparatus using the developer.

  The present invention includes a carrier core material and a resin coating layer, the carrier shape factor SF1 is 125 or less, the number of exposed carrier core materials on the carrier surface is 10 to 60, and the exposed carrier core Among the materials, those having a ferret horizontal diameter in the range of 1 μm or more and 3 μm or less are 80 number% or more of electrostatic charge image developing carriers.

  The present invention also provides an electrostatic charge image developing developer comprising the electrostatic charge image developing carrier and the electrostatic charge image developing toner.

  The present invention also provides an image carrier, latent image forming means for forming an electrostatic latent image on the surface of the image carrier, and developing the electrostatic latent image using a developer to form a toner image. A developing unit; a transferring unit that transfers the developed toner image to a transfer target; and a cleaning unit that removes a residue remaining on the surface of the image holding member. The image forming apparatus is a developer for developing a charge image, wherein the cleaning unit includes an elastic blade, and the elastic resilience of the elastic blade is 60% to 75%.

  According to claim 1 of the present invention, when the carrier shape factor SF1, the number of exposed carrier cores, and the number% of the exposed carrier cores whose ferret horizontal diameter is in the range of 1 μm to 3 μm is outside this range. Compared to the above, it is possible to provide a carrier for developing an electrostatic charge image that can suppress generation of streak-like image defects and obtain a good image even when low-speed printing and high-speed printing are alternately repeated. .

  According to claim 2 of the present invention, when the shape factor SF1 of the carrier, the number of exposed carrier core materials, and the number% of the exposed carrier core materials whose ferret horizontal diameter is in the range of 1 μm to 3 μm is out of this range. Compared to the above, it is possible to provide a developer for developing an electrostatic charge image that can suppress generation of streak-like image defects and obtain a good image even when low-speed printing and high-speed printing are alternately repeated. it can.

  According to claim 3 of the present invention, compared to the case where the rebound resilience of the elastic blade is outside this range, the occurrence of streak-like image defects is suppressed even when low-speed printing and high-speed printing are repeated alternately, An image forming apparatus capable of obtaining a good image can be provided.

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

<Carrier for developing electrostatic image>
The electrostatic image developing carrier according to the present embodiment includes a carrier core material and a resin coating layer, the carrier has a shape factor SF1 of 125 or less, and the number of exposed carrier core materials on the carrier surface is 10 or more and 60. Among the exposed carrier core materials, those having a ferret horizontal diameter in the range of 1 μm to 3 μm are 80% by number or more.

  An electrophotographic image forming apparatus such as a printer or a copying machine may operate at a low speed for color printing using OHP or cardboard, for example, after performing high-speed printing in black and white. At this time, residuals such as toner and carrier accumulate in a dense space between the cleaning means such as a cleaning blade and the photosensitive member. In particular, when high-speed printing and low-speed printing are repeated in a low toner concentration, high-temperature, high-humidity environment, scattering of the carrier onto the photoconductor increases, and the carrier deposition rate increases.

  If the carrier is deformed (in the direction in which the shape factor SF1 is large), the photoconductor is damaged when the acute angle portion of the carrier contacts the photoconductor, and the friction increases when the flat surface of the carrier contacts the photoconductor. , Chipping of the cleaning blade is likely to occur. On the other hand, when the carrier is spherical (in the direction in which the shape factor SF1 is close to 100), it is easy to be packed most closely when it accumulates between the cleaning blade and the photoconductor, and the photoconductor when repeating low-speed printing and high-speed printing. A cleaning defect may occur due to scratches on the surface or the cleaning blade being pushed up.

  The present inventors have exposed the carrier shape factor SF1 of 125 or less and the number of exposed carrier cores on the carrier surface of 10 or more and 60 or less as in the electrostatic charge image developing carrier according to this embodiment. Among the carrier core materials, those having a ferret horizontal diameter in the range of 1 μm or more and 3 μm or less are 80% by number or more, because the contact area of the carrier deposit with the photosensitive member is small and dense deposition becomes difficult. It was found that cleaning properties were obtained and streak image defects were less likely to occur. In other words, if it is within these ranges, it is difficult for the photoconductor to be scratched, and residuals such as toner and carrier are difficult to pass through the cleaning blade, so that it is easy to be cleaned, and the cleaning property with respect to changes in the printing speed is improved. A streak-like image defect is difficult to occur in repeated high-speed printing.

  In the electrostatic charge image developing carrier according to this embodiment, the shape factor SF1 of the carrier is 125 or less, and preferably 120 or less. When the shape factor SF1 of the carrier exceeds 125, the contact area between the carrier and the photoconductor increases, so that the photoconductor is scratched, the cleaning blade is missing, or the toner is removed from the cleaning blade. Further, the shape factor SF1 is preferably 115 or more.

  The number of exposed carrier core materials on the carrier surface is 10 or more and 60 or less, and preferably 15 or more and 40 or less. When the number of exposed carrier core materials on the carrier surface is less than 10, the carrier deposit tends to become dense, and the cleaning blade is missing or toner is lost. If the number of exposed carrier core materials on the carrier surface exceeds 60, the photoconductor is scratched because there are too many contact points of the carrier core material with the photoconductor.

  Among the exposed carrier core materials, those having a ferret horizontal diameter in the range of 1 μm to 3 μm are 80% by number or more, preferably 85% by number or more. When it is less than 80% by number, the effect of exposing the carrier core material is not exhibited. Further, if the exposed carrier core material has a ferret horizontal diameter of less than 1 μm, the effect of exposing the carrier core material is not exhibited, and if it exceeds 3 μm, resistance to the cleaning blade due to the engagement of the convex portions of the carrier core material is reduced. Strengthens and causes poor cleaning.

  In the present embodiment, the number of exposed carrier core materials on the surface of the carrier and the ferret horizontal diameter of the exposed carrier core materials indicate that the exposed portion of the core material has an appropriate size and an appropriate amount on the carrier surface. By doing so, scratches on the photoreceptor are prevented. When this is expressed by the exposed area of the core material on the surface of the carrier, when the exposed portion having a large area collides with the surface of the photoconductor, the photoconductor is easily damaged. Therefore, a preferable state can be maintained by setting the number of exposed portions, not the area, and the ferret horizontal diameter of the exposed portions in a certain range.

  The carrier of this embodiment can be manufactured as follows, for example. First, as the carrier core material, the surface roughness, for example, the average interval Sm of unevenness is 1 μm or more and 5 μm or less, the arithmetic average roughness Ra is 0.4 or more and 1.0 or less, and the standard deviation of Sm is 1.3 or less Is preferably used.

  Examples of methods for producing a carrier core material having a carrier core surface roughness Sm of 1 μm or more and 5 μm or less, Ra of 0.4 or more and 1.0 or less, and a standard deviation of Sm of 1.3 or less are as follows. Mix an appropriate amount, pulverize and mix in a wet ball mill for 8 hours to 35 hours, granulate and dry with a spray dryer, etc., then use a rotary kiln or the like at 800 ° C to 1100 ° C for 8 hours to 10 hours. Hereinafter, temporary firing is performed. Temporary baking is performed once or more and three times or less as necessary. Thereafter, the temporarily fired product is dispersed in water and pulverized with a wet ball mill or the like until the volume average particle size becomes 0.3 μm or more and 1.0 μm or less. This slurry is granulated and dried using a spray dryer, etc., for the purpose of adjusting the magnetic properties and resistance, while firing at a temperature of 1000 ° C. to 1300 ° C. for 6 hours to 10 hours while controlling the oxygen concentration, pulverizing, Further, it can be obtained by classification into a desired particle size distribution. In the present embodiment, it is preferable to use a rotary electric furnace in order to make the core surface shape uniform.

  At this time, the particle size of the pulverized slurry is adjusted so that the number distribution is 0.1% or less and 1.2 μm or more, respectively, and the number distribution is 2% or less, and the oxygen concentration and the firing temperature are optimized according to the composition of the metal oxide. By doing so, a carrier core material having a desired surface roughness can be obtained.

  The surface roughness, Sm, and Ra of the carrier core material can be measured with an ultra-depth color 3D shape measurement microscope (VK-9500, manufactured by Keyence Corporation) in accordance with JIS B0601.

  Next, when the Ra of the carrier core material is in the range of 0.6 to 1.0, using a fluidized bed, a powder coat, etc., gradually observing the exposed state of the carrier core material on the surface, A coating agent (solution for forming a resin coating layer) containing a coating solvent or the like is applied repeatedly. At this time, the surface can be observed by sampling at regular intervals and using a FE-SEM. Further, when coating, if it is a fluidized bed, the initial coating amount of the coating agent can be reduced, and the intended carrier surface can be obtained by gradually increasing the coating amount of the coating agent. In the powder coating, the particle size of the coated particles is set to be equal to or less than the maximum value of Sm of the carrier core material, and about one third of the coated particle amount to be the target coating is first coated, and then the remaining 3 The carrier according to the present embodiment can be obtained by covering about two minutes.

  A method in which Ra of the carrier core material is in the range of 0.4 or more and less than 0.6 is preferably coated under a reduced pressure such as a kneader coater. At that time, it is preferable that the stirring speed is high and the pressure reduction is high. Furthermore, after charging the carrier core material and the coating agent, the mixture is stirred for about 1 hour or more at a temperature higher than the glass transition point Tg of the coating resin and lower than the boiling point of the coating solvent contained in the coating agent, and then depressurized. The carrier according to the present embodiment can be obtained by raising the temperature.

As the carrier core material, any conventionally known material can be used, but ferrite and magnetite are particularly preferably selected. For example, iron powder is known as another carrier core material. In the case of iron powder, since the specific gravity is large and the toner is likely to be deteriorated, ferrite and magnetite are more stable. An example of ferrite is generally represented by the following formula.
(MO) _X (Fe ₂ O ₃ ) _Y
(In the formula, M contains at least one selected from Cu, Zn, Fe, Mg, Mn, Ca, Li, Ti, Ni, Sn, Sr, Al, Ba, Co, Mo, etc. X, Y represents a weight mol ratio and satisfies the condition X + Y = 100).

The M is preferably a ferrite particle which is one or a combination of Li, Mg, Ca, Mn, Sr and Sn, and the content of other components is 1% by weight or less. By adding Cu, Zn and Ni elements, the resistance tends to be low, and charge leakage tends to occur. In addition, the resin tends to be difficult to coat, and the environmental dependency tends to deteriorate. Furthermore, since it is a heavy metal, the stress given to a carrier becomes strong and may have a bad influence with respect to preservability. In recent years, from the viewpoint of safety, an element containing Mn element or Mg element has been widely used. Ferrite core material is suitable. As raw material for carrier core material, Fe ₂ O ₃ is an essential component, and as magnetic particles used, ferromagnetic iron oxide particles such as magnetite and maghemite, metals other than iron (Mn , Ni, Zn, Mg, Cu, etc.) spinel ferrite particle powder containing one or more types, magnet plumbite type ferrite particle powder such as barium ferrite, and iron or iron alloy particle powder having an oxide film on its surface Can be used.

  Specific examples of the carrier core material include iron-based oxides such as magnetite, γ-iron oxide, Mn—Zn ferrite, Ni—Zn ferrite, Mn—Mg ferrite, Li ferrite, and Cu—Zn ferrite. You can list things. Among these, inexpensive magnetite can be used more preferably.

  The carrier core material may be a resin-dispersed carrier core material in which the magnetic particles (magnetic material) are dispersed in a binder resin.

  As the binder resin, a phenol resin, a melamine resin, an epoxy resin, a urethane resin, a polyester resin, a silicone resin, or the like is used, but a phenol resin is preferably included. By using a phenol-based resin, adhesion with the coating resin is improved, and long-term stability is further improved.

  At this time, the target surface state can be obtained by making the volume average particle diameter of the magnetic material in the binder resin uniform within a range of 5 μm or more and 10 μm or less, increasing the magnetic material ratio, and appropriately exposing the magnetic material.

  Examples of the coating resin used for the resin coating layer include polyolefin resins such as polyethylene, polypropylene; polyvinyl and polyvinylidene resins such as polystyrene, acrylic resin, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, and polyvinyl carbazole. , Polyvinyl ether and polyvinyl ketone; vinyl chloride / vinyl acetate copolymer; styrene / acrylic copolymer; straight silicone resin composed of organosiloxane bond or modified product thereof; fluororesin such as polytetrafluoroethylene, polyvinyl fluoride, Polyvinylidene fluoride, polychlorotrifluoroethylene; polyester; polyurethane; polycarbonate, amino resin such as urea-formaldehyde Fats; epoxy resins; perfluoroalkyl (meth) acrylate / (meth) acrylate copolymer, and the like. These may be used alone or in combination with a plurality of resins. Of these, styrene / acrylic copolymers and perfluoroalkyl (meth) acrylate / (meth) acrylate copolymers are preferred from the viewpoints of carrier charge imparting property and charge maintaining property.

  The resin coating layer may contain a negative charge control agent. Negative charge control agents include trimethylethane dyes, metal complexes of salicylic acid, metal complexes of benzylic acid, copper phthalocyanine, perylene, quinacridone, azo pigments, metal complex azo dyes, azochrome complexes, etc. Examples thereof include dyes, calixarene type phenolic condensates, cyclic polysaccharides, resins containing a carboxyl group and / or a sulfonyl group.

  The content of the negative charge control agent is preferably in the range of 0.001 wt% to 1.0 wt% with respect to the weight of the carrier core material, 0.01 wt% to 0.8 wt%. The following range is more preferable. If the content of the negative charge control agent is less than 0.001% by weight with respect to the weight of the carrier core material, there may be no effect on the toner charge rising property. May inhibit the charging ability.

  The resin coating layer of the carrier may be used in combination with conductive powder (conductive particles) for further carrier resistance adjustment. Examples of the conductive particles include metal powder, carbon black, titanium oxide, tin oxide, and zinc oxide. These conductive particles preferably have a volume average particle diameter of 1 μm or less. When the volume average particle diameter is larger than 1 μm, it is difficult to control the dispersion of the powder in the resin coating layer, and it may be difficult to control the electric resistance. The addition amount of the conductive particles is preferably less than 20% by volume of the resin coating layer. When 20 volume% or more is added, it is difficult to control the dispersion of the powder in the resin coating layer, and it may be difficult to control the electric resistance. Examples of the method for dispersing the conductive particles include a sand mill, a dyno mill, and a homomixer.

  Further, the resin coating layer of the carrier may contain a wax. Waxes are hydrophobic, are relatively soft at room temperature, and have low film strength. This originates from the molecular structure of the wax. However, if wax is present in the resin coating layer for this property, toner components such as external additives added to the toner surface or toner bulk components are present on the carrier surface. Hard to adhere. Even if it adheres, the surface of the carrier is renewed by peeling off the wax at the adhesion level at the molecular level, and the carrier surface is not easily contaminated.

  The wax is not particularly limited, and examples thereof include paraffin wax and derivatives thereof, montan wax and derivatives thereof, microcrystalline wax and derivatives thereof, Fischer-Tropsch wax and derivatives thereof, and polyolefin wax and derivatives thereof. Derivatives include oxides, polymers with vinyl monomers, and graft modified products. In addition, alcohols, fatty acids, plant waxes, animal waxes, mineral waxes, ester waxes, acid amides, and the like can be used. Other known materials can also be used. The melting point of the wax is preferably 60 ° C. or higher and 200 ° C. or lower. More preferably, the melting point of the wax is 80 ° C. or higher and 150 ° C. or lower. If it is less than 60 degreeC, the fluidity | liquidity as a carrier will deteriorate.

  The thickness of the resin coating layer is preferably in the range of 0.1 μm to 5 μm, and more preferably in the range of 0.2 μm to 3 μm. If the thickness of the resin coating layer is smaller than 0.1 μm, it may be difficult to form a uniform and flat resin coating layer on the surface of the carrier core material. On the other hand, if the thickness is larger than 5 μm, carriers may be aggregated and it may be difficult to obtain a uniform carrier.

<Developer for developing electrostatic image>
The developer for developing an electrostatic charge image according to the exemplary embodiment includes a toner and a carrier, and the carrier is the carrier for developing an electrostatic charge image. That is, the developer for developing an electrostatic charge image according to the exemplary embodiment is a two-component developer including a toner and a carrier.

  The toner is not particularly limited, and a known toner containing a binder resin and a colorant as main components and containing a release agent or the like as necessary can be used. The toner may be produced by a dry production method such as a kneading and pulverization method, or may be produced by a wet production method such as an emulsion polymerization aggregation method, a dissolution suspension method, or a suspension polymerization method. . A toner produced by an emulsion polymerization aggregation method is preferred from the standpoint that the surface exposure of the colorant and the release agent is small and the stability of the image is good.

  Such a toner has a relatively round particle shape, a narrow particle size distribution, a relatively uniform toner surface, high chargeability, and a narrow charge distribution. Since this toner has a narrow particle size distribution, the occurrence of fogging is small.

  As the binder resin for the toner, styrenes such as styrene and chlorostyrene; monoolefins such as ethylene, propylene, butylene, and isobutylene; vinyl acetate, vinyl propionate, vinyl benzoate, vinyl butyrate, methyl acrylate, acrylic acid Esters of α-methylene aliphatic monocarboxylic acids such as ethyl, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate; vinyl methyl ether, Examples include vinyl ethers such as vinyl ethyl ether and vinyl butyl ether; homopolymers or copolymers such as vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, and vinyl isopropenyl ketone. Examples of the binder resin include polystyrene, styrene / alkyl acrylate copolymer, styrene / alkyl methacrylate copolymer, styrene / acrylonitrile copolymer, styrene / butadiene copolymer, styrene / maleic anhydride copolymer, Examples thereof include polyethylene and polypropylene. Further examples include polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin waxes and the like.

  Examples of the colorant include carbon black, chrome yellow, hansa yellow, benzidine yellow, sren yellow, quinoline yellow, permanent orange GTR, pyrazolone orange, vulcan orange, watch young red, permanent red, brillianthamine 3B, and brillianthamine. 6B, DuPont Oil Red, Pyrazolone Red, Resol Red, Rhodamine B Lake, Lake Red C, Rose Bengal, Aniline Blue, Ultramarine Blue, Calco Oil Blue, Methylene Blue Chloride, Phthalocyanine Blue, Phthalocyanine Green, Malachite Green Oxalate, etc. Or acridine, xanthene, azo, benzoquinone, azine, anthraquinone, thio Various dyes such as Ndico, Dioxazine, Thiazine, Azomethine, Indico, Thioindico, Phthalocyanine, Aniline Black, Polymethine, Triphenylmethane, Diphenylmethane, Thiazine, Thiazole, and Xanthene Or in combination of two or more.

  In the toner according to the exemplary embodiment, the content of the colorant is preferably in the range of 1 part by weight to 30 parts by weight with respect to 100 parts by weight of the binder resin. It is also effective to use a surface-treated colorant or a pigment dispersant. By appropriately selecting the type of the colorant, yellow toner, magenta toner, cyan toner, black toner and the like can be obtained.

  Examples of mold release agents include low molecular weight polyolefins such as polyethylene, polypropylene and polybutene; silicones having a softening point upon heating; fatty acid amides such as oleic acid amide, erucic acid amide, ricinoleic acid amide and stearic acid amide; Plant waxes such as ester wax, carnauba wax, rice wax, candelilla wax, tree wax, jojoba oil, etc .; animal waxes such as beeswax; montan wax, ozokerite, ceresin, paraffin wax, microcrystalline wax, fisher Mineral waxes such as Tropsch wax, petroleum waxes, and modified products thereof can be used. The addition amount of the release agent can be added in the range of 50% by weight or less with respect to the toner.

  As other internal additives, magnetic materials such as metals such as ferrite, magnetite, reduced iron, cobalt, nickel and manganese, alloys thereof, and compounds containing these metals can be used. As the charge control agent, various commonly used charge control agents such as quaternary ammonium salts, nigrosine compounds, dyes composed of complexes of aluminum, iron, chromium, and triphenylmethane pigments can be used. In order to control the ionic strength that affects the stability at the time of aggregation and fusion integration and to reduce wastewater contamination, a charge control agent that is difficult to dissolve in water is preferable.

  Examples of inorganic particles to be wet-added include silica, alumina, titania, calcium carbonate, magnesium carbonate, and tricalcium phosphate, all of which are usually used as external additives on the toner surface, such as ionic surfactants and It can be dispersed in a polymer acid or a polymer base and wet-added.

  Surfactants used for emulsion polymerization, seed polymerization, pigment dispersion, resin particle dispersion, release agent dispersion, aggregation, or stabilization in the toner manufacturing process by a wet manufacturing method include sulfate ester salts, sulfonate salts, phosphorus Examples thereof include anionic surfactants such as acid esters and soaps, and cationic surfactants such as amine salts and quaternary ammonium salts, and also polyethylene glycols, alkylphenol ethylene oxide adducts, polyhydric alcohols. It is also effective to use a nonionic surfactant such as a system together.

  Further, the external additive used in the present embodiment is not particularly limited, and known external additives such as inorganic particles and organic particles can be used. Among them, silica, titania, alumina, cerium oxide, titanium, and the like can be used. Organic particles such as inorganic particles such as strontium acid, calcium carbonate, magnesium carbonate and calcium phosphate, metal soap such as zinc stearate, fluorine-containing resin particles, silica-containing resin particles and nitrogen-containing resin particles are preferred. Moreover, you may surface-treat on the surface of an external additive according to the objective. Examples of the surface treatment agent include a silane compound, a silane coupling agent, and a silicone oil for performing a hydrophobic treatment.

  The volume average particle size of the toner according to the exemplary embodiment is preferably in the range of 4 μm to 8 μm, and more preferably in the range of 5 μm to 7 μm. If the volume average particle diameter of the toner is less than 4 μm, the amount of fine powder increases, so that toner fog and poor cleaning are likely to occur.

  In addition, the volume average particle size distribution index GSDv of the toner according to the exemplary embodiment is preferably in the range of 1.0 to 1.3, more preferably in the range of 1.1 to 1.3. More preferably, it is in the range of 1.15 or more and 1.24 or less. When the GSDv exceeds 1.3, the presence of coarse particles and fine powder particles increases, so that the aggregation of the toners becomes intense, and it becomes easy to cause charging failure and transfer failure. Moreover, when GSDv is less than 1.1, it will be quite difficult to manufacture.

The volume average particle size D50v and the volume average particle size distribution index GSDv can be obtained by measuring with an aperture diameter of 100 μm using a Coulter Multisizer II type (manufactured by Beckman Coulter, Inc.). At this time, the measurement is performed after the toner is dispersed in an electrolyte aqueous solution (Isoton II aqueous solution) and dispersed by ultrasonic waves for 30 seconds or more. For the particle size range (channel) divided based on the measured particle size distribution of the toner, a cumulative distribution is drawn from the small diameter side for each of the volume and number, and the particle size that becomes 16% is the volume D16v and the cumulative is 50%. The particle diameter to be defined is defined as volume D50v, and the particle diameter to be accumulated 84% is defined as volume D84v. At this time, D50v represents the volume average particle diameter, and the volume average particle size distribution index (GSDv) is obtained as (D84v / D16v) ^1/2 .

  In addition, the toner shape factor SF1 represented by the following formula of the toner for developing an electrostatic charge image according to the exemplary embodiment is preferably in the range of 110 to 140, and more preferably in the range of 115 to 135. More preferably, it is in the range of 120 to 130. If the toner shape factor SF1 is less than 110, the toner particles are close to a spherical shape, which may cause a cleaning failure after transfer. On the other hand, when the toner shape factor SF1 exceeds 140, not only the transfer efficiency and the image quality are deteriorated, but also the shape range of the toner particles obtained by a low-temperature manufacturing method may be exceeded.

SF1 = (ML ² / A) × (π / 4) × 100
(In the above formula, ML represents the maximum length (μm) of the toner, and A represents the projected area (μm ² ) of the toner.

  The toner shape factor SF1 can be measured as follows using a Luzex image analyzer (manufactured by Nireco Corporation, FT). First, an optical microscope image of the toner spread on the slide glass is taken into a Luzex image analyzer through a video camera, and the maximum length (ML) and the projected area (A) of 50 toners are measured. SF1 is calculated, and an average of these can be obtained as the toner shape factor SF1.

  The ratio of the toner in preparing the developer by mixing the toner and the carrier is in the range of 1 to 15% by weight, preferably 3 to 12% by weight of the whole developer.

If the toner ratio is less than 1% by weight, it is difficult to obtain a sufficient image density, and a solid image is difficult to be uniform. On the other hand, if the amount exceeds 15% by weight, the toner coverage on the carrier surface exceeds 100%, and the charge amount decreases (when the average value of the average charge amount is less than 15 μC / g). Fog) High-quality color images cannot be obtained. For example, if the amount exceeds 15% by weight, the toner coverage on the carrier surface approaches 100%, so that the resistance value as a developer is extremely increased, and 1 × 10 ⁵ Ω · cm or more and 1 × 10 ⁸ Ω · cm or less. This makes it difficult to fit within the range, and it is difficult to obtain a good and high-quality color image such as blurring of the image edge portion.

  However, in a low-humidity environment, if the toner ratio is less than 1% by weight, a high charge amount (the absolute value of the average charge amount exceeds 25 μC / g) tends to occur, and it may be difficult to obtain a sufficient image density. Therefore, it is preferable to select the toner ratio so that the absolute value of the charging property is in the range of 15 to 50 μC / g depending on the environment.

<Image forming apparatus>
The image forming apparatus according to the present embodiment includes an image carrier, latent image forming means for forming an electrostatic latent image on the surface of the image carrier, and developing the electrostatic latent image with a developer to form a toner image. A developing unit that forms the toner image, and a transfer unit that transfers the developed toner image to the transfer target. The developer for developing an electrostatic charge image is used as the developer. In addition, the image forming apparatus according to the present embodiment includes means other than those described above, for example, charging means for charging the image holding member, fixing means for fixing the toner image transferred to the surface of the transfer target, and the surface of the image holding member. Further, it may include a cleaning means for removing the remaining toner, carrier and the like. In this embodiment, it is preferable that the cleaning unit includes an elastic blade, and the rebound resilience of the elastic blade is 60% or more and 75% or less.

  An example of the image forming apparatus according to the present embodiment is schematically shown in FIG. The image forming apparatus 1 includes a charging unit 10, an exposure unit 12, an electrophotographic photosensitive member 14 that is an image holding member, a developing unit 16, a transfer unit 18, a cleaning unit 20, and a fixing unit 22.

  In the image forming apparatus 1, the charging unit 10 that is a charging unit that charges the surface of the electrophotographic photosensitive member 14 and the charged electrophotographic photosensitive member 14 are exposed around the electrophotographic photosensitive member 14 according to image information. The exposure unit 12 is a latent image forming unit that forms an electrostatic latent image, the developing unit 16 is a developing unit that develops the electrostatic latent image with toner to form a toner image, and the surface of the electrophotographic photoreceptor 14. A transfer unit 18 that is a transfer unit that transfers the toner image formed on the surface of the transfer target 24, and a cleaning unit 20 that is a cleaning unit that removes toner remaining on the surface of the electrophotographic photosensitive member 14 after transfer. Are arranged in this order. A fixing unit 22 that is a fixing unit that fixes the toner image transferred to the transfer target 24 is arranged on the left side of the transfer unit 18.

  An operation of the image forming apparatus 1 according to the present embodiment will be described. First, the surface of the electrophotographic photosensitive member 14 is uniformly charged by the charging unit 10 (charging process). Next, light is applied to the surface of the electrophotographic photosensitive member 14 by the exposure unit 12, and the charged charges in the irradiated portion are removed, and an electrostatic charge image (electrostatic latent image) is formed according to the image information. (Latent image forming step). Thereafter, the electrostatic charge image is developed by the developing unit 16, and a toner image is formed on the surface of the electrophotographic photosensitive member 14 (developing step). For example, in the case of a digital electrophotographic copying machine using an organic photoconductor as the electrophotographic photoconductor 14 and using a laser beam as the exposure unit 12, the surface of the electrophotographic photoconductor 14 is negatively charged by the charging unit 10. Then, a digital latent image is formed in a dot shape by the laser beam light, and toner is applied to the portion irradiated with the laser beam light by the developing unit 16 to be visualized. In this case, a negative bias is applied to the developing unit 16. Next, a transfer member 24 such as paper is superposed on the toner image at the transfer unit 18, and a charge opposite in polarity to the toner is applied to the transfer member 24 from the back side of the transfer member 24, and the toner image is generated by electrostatic force. Is transferred to the transfer target 24 (transfer process). The transferred toner image is heated and pressed by a fixing member in the fixing unit 22 and is fused and fixed to the transfer target 24 (fixing step). On the other hand, toner remaining on the surface of the electrophotographic photoreceptor 14 without being transferred is removed by the cleaning unit 20 (cleaning step). One cycle is completed in a series of processes from charging to cleaning. In FIG. 1, the toner image is directly transferred to the transfer target 24 such as a sheet by the transfer unit 18, but may be transferred via a transfer member such as an intermediate transfer member.

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

(Charging means)
For example, a charging device such as a corotron as shown in FIG. 1 is used as the charging unit 10 as a charging unit, but a conductive or semiconductive charging roll may be used. A contact charger using a conductive or semiconductive charging roll may apply a direct current to the electrophotographic photosensitive member 14 or may superimpose an alternating current. For example, the charging unit 10 charges the surface of the electrophotographic photosensitive member 14 by generating a discharge in a minute space near the contact portion with the electrophotographic photosensitive member 14. Normally, it is charged to −300V or more and −1000V or less. The conductive or semiconductive charging roll may have a single layer structure or a multiple structure. Further, a mechanism for cleaning the surface of the charging roll may be provided.

(Image carrier)
The image carrier has a function of forming at least a latent image (electrostatic charge image). As the image carrier, an electrophotographic photosensitive member is preferably exemplified. The electrophotographic photoreceptor 14 has a coating film containing an organic photoreceptor or the like on the outer peripheral surface of a cylindrical conductive substrate. The coating film is a substrate in which a subbing layer and a photosensitive layer including a charge generating layer containing a charge generating material and a charge transporting layer containing a charge transporting material are formed in this order on the substrate as necessary. is there. The order of stacking the charge generation layer and the charge transport layer may be reversed. These are laminated photoconductors in which a charge generation material and a charge transport material are contained in separate layers (charge generation layer, charge transport layer), but both the charge generation material and the charge transport material are the same. A single-layer type photoreceptor included in the above layer may be used, and a laminated photoreceptor is preferable. Further, an intermediate layer may be provided between the undercoat layer and the photosensitive layer. In addition, other types of photosensitive layers such as an amorphous silicon photosensitive film may be used in addition to the organic photoreceptor.

(Exposure means)
There are no particular limitations on the exposure unit 12 that is an exposure means. For example, an optical device that can expose a light source such as semiconductor laser light, LED light, or liquid crystal shutter light on the surface of the image carrier in a desired image-like manner. Can be mentioned.

(Development means)
The developing unit 16 serving as a developing unit has a function of developing a latent image formed on the image carrier with a developer containing toner to form a toner image. Such a developing device is not particularly limited as long as it has the above-mentioned function, and can be appropriately selected according to the purpose. For example, toner for developing an electrostatic image is used using a brush, a roller, or the like. A known developing device having a function of adhering to the electrophotographic photosensitive member 14 may be used. For the electrophotographic photosensitive member 14, a DC voltage is usually used, but an AC voltage may be superimposed and used.

(Transfer means)
As the transfer unit 18 serving as a transfer unit, for example, a charge having a polarity opposite to that of the toner is applied to the transfer target 24 from the back side of the transfer target 24 as shown in FIG. A transfer roll and a transfer roll pressing device using a conductive roll or a semiconductive roll that transfers directly to the surface of the transferred body 24 via the transferred body 24 can be used. . A direct current may be applied to the transfer roll as a transfer current applied to the image carrier, or an alternating current may be applied in a superimposed manner. The transfer roll can be arbitrarily set depending on the width of the image area to be charged, the shape of the transfer charger, the opening width, the process speed (circumferential speed), and the like. Further, a single layer foam roll or the like is suitably used as a transfer roll for cost reduction. As a transfer method, a method of transferring directly to the transfer target 24 such as paper or a method of transferring to the transfer target 24 via an intermediate transfer member may be used.

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

(Cleaning means)
The cleaning unit 20 serving as a cleaning unit may be appropriately selected such as one that employs a blade cleaning method, a brush cleaning method, or a roll cleaning method as long as the toner remaining on the image carrier is cleaned. Among these, it is preferable to use a cleaning blade having elasticity.

  In the present embodiment, the resilience of the cleaning blade is preferably 60% or more and 75% or less. When the rebound resilience of the cleaning blade is 60% or more and 75% or less, problems caused by repeated low-speed printing and high-speed printing are unlikely to occur with respect to blade turning over deposits. If the impact resilience of the cleaning blade is less than 60%, the blade may turn up. If the resilience of the cleaning blade exceeds 75%, the cleaning blade may be chipped.

  When the rebound resilience of the cleaning blade is within this range, the cleaning property is good, and scratches on the blade and the photosensitive member, which are problems when the cleaning blade is made highly repellent, are difficult to occur.

  A specific method for measuring the impact resilience conforms to the Lücke-type impact resilience test of the impact resilience test method for JIS K6255 vulcanized rubber and thermoplastic rubber. When measuring the impact resilience, the sample to be measured should be in advance at that temperature (when the impact resilience at 10 ° C is measured, in a 10 ° C environment) so that the sample is at the temperature of the measurement conditions at the time of measurement. It is desirable to leave the sample sufficiently.

  The material of the cleaning blade is not particularly limited as long as it is an elastic body that satisfies the above physical properties, and various elastic bodies can be used. Specific elastic bodies include elastic bodies such as polyurethane elastic bodies, silicone rubber, and chloroprene rubber. Among them, it is preferable to use a polyurethane elastic body because of its excellent wear resistance.

  As the polyurethane elastic body, generally used is a polyurethane synthesized through an addition reaction of an isocyanate with a polyol and various hydrogen-containing compounds. This uses a polyether polyol such as polypropylene glycol or polytetramethylene glycol as a polyol component, or a polyester polyol such as an adipate polyol, polycaprolactam polyol or polycarbonate polyol, and a tolylene diisocyanate as an isocyanate component. Using aromatic polyisocyanates such as 4,4′-diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, toluidine diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, dicyclohexylmethane diisocyanate, etc. Prepare a urethane prepolymer, add a curing agent to it, and inject into a predetermined mold , After crosslinking and curing, it is prepared by aging at room temperature. As the curing agent, a dihydric alcohol such as 1,4-butanediol and a trihydric or higher polyhydric alcohol such as trimethylolpropane or pentaerythritol are usually used in combination.

(Fixing means)
The fixing unit 22 that is a fixing unit (image fixing device) fixes the toner image transferred to the transfer medium 24 by heating, pressing, or heating and pressing, and includes a fixing member.

(Transfer)
Examples of the transfer target (paper) 24 to which the toner image is transferred include plain paper, OHP sheet, and the like used in electrophotographic copying machines, printers, and the like. In order to further improve the smoothness of the image surface after fixing, it is preferable that the surface of the transfer target is as smooth as possible. For example, coated paper in which the surface of plain paper is coated with resin, art paper for printing, etc. Can be preferably used.

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

(Parameter measurement method)
(1) Shape factor SF1
The shape factor SF1 is an average value of the shape factors, and is calculated by the following method. The optical microscope image of the carrier dispersed on the slide glass is taken into a Luzex image analyzer through a video camera, and SF1 is obtained from the perimeter and the projected area for 100 carriers by the following formula to obtain an average value. The shape factor SF1 of the carrier in the developer is determined by putting the developer in water containing a surfactant, separating the toner and the carrier with ultrasonic waves, and then taking out only the carrier with a magnet and performing the image analysis. Was determined by
SF1 = (ML) ² / A × (100 / 4π)
(In the formula, ML represents the perimeter of the carrier particles, and A represents the projected area of the carrier particles.)

(2) Number of exposed carrier core materials Similar to the measurement of the shape factor SF1, the optical microscope image of the carrier is taken into the Luzex image analyzer, and the contrast between the exposed portion of the carrier core material and the coating layer portion is changed. The number of exposures per carrier particle is obtained. Measurement is performed on 100 carriers, and the average value is defined as the number of exposed core materials. The number of exposed carrier core materials in the developer was determined in the same manner as SF1.

(3) Ratio of exposed carrier core material having a ferret horizontal diameter of 1 μm or more and 3 μm or less In the same manner as the measurement of the shape factor SF1, an optical microscope image of the carrier is taken into the Luzex image analyzer, and the ferret horizontal diameter of the exposed portion of the carrier core material Is calculated from the ratio of the number of exposed parts in the range of 1 μm to 3 μm and the total number of exposed parts. The ratio of the exposed carrier core material (ferret horizontal diameter of 1 μm or more and 3 μm or less) of the carrier in the developer was determined in the same manner as SF1.

(Carrier core 1)
72 parts by weight of Fe ₂ O ₃ , 20 parts by weight of MnO _{2 and} 8 parts by weight of Mg (OH) ₂ were mixed, mixed with cellulose resin as a binder, mixed for 25 hours in a wet ball mill, granulated and dried by a spray dryer. Then, temporary baking was performed at 1000 ° C. for 7 hours using a rotary kiln. The calcined product thus obtained was pulverized with a wet ball mill for 30 hours and sieved with a 16 μm sieving mesh. Further, it is processed by centrifugation until the ratio of particles having a particle size of 1.2 μm or more and 0.3 μm or less is less than 2%, then granulated and dried by a spray dryer, and then subjected to a temperature of 1100 ° C. in an electric furnace. The main baking was performed for 9 hours. At this time, the oxygen concentration was 4%. Ferrite particles 1 having a particle size of 36 μm were prepared through a crushing step and a classification step. The obtained ferrite particles had SF1 of 116, Sm of 3 μm, Sm standard deviation of 1.0, and Ra of 0.5 μm.

(Carrier core 2)
A carrier core material 2 was produced in the same manner as in the carrier core material 1 except that the pulverization time of the temporarily fired product by a wet ball mill was set to 35 hours. The obtained ferrite particles had a particle size of 35 μm, SF1 of 116, Sm of 5 μm, Sm standard deviation of 1.2, and Ra of 0.5 μm.

(Carrier core 3)
A carrier core material 3 was produced in the same manner as in the carrier core material 1 except that the main firing temperature was 1150 ° C. and the time was 8 hours. The obtained ferrite particles had a particle size of 36 μm, SF1 of 120, Sm of 5 μm, Sm standard deviation of 1.2, and Ra of 0.8 μm.

(Carrier core 4)
In the carrier core material 1, the carrier core material 4 is produced in the same manner except that the pulverization time of the pre-fired product by a wet ball mill is 20 hours, centrifugation is not performed, the main firing temperature is 1200 ° C., and the time is 8 hours. did. The obtained ferrite particles had a particle size of 36 μm, SF1 of 138, Sm of 7 μm, Sm standard deviation of 1.5, and Ra of 0.2 μm.

(Carrier core 5)
A carrier core material 5 was prepared in the same manner as in the carrier core material 1 except that the main firing temperature was 1180 ° C., the time was 10 hours, and the oxygen concentration was 3%. The obtained ferrite particles had a particle size of 36 μm, SF1 of 116, Sm of 8 μm, Sm standard deviation of 1.3, and Ra of 1.0 μm.

(Preparation of resin coating layer forming solution)
Styrene acrylic resin (styrene / methylmethacrylic acid copolymer, molar ratio 79:21:20, Tg 70 ° C.) 30 parts by weight Carbon black (VXC72, manufactured by Cabot) 4 parts by weight Toluene 250 parts by weight Isopropyl alcohol 50 parts by weight And glass beads (particle size: 1 mm, the same amount as toluene) were put into a sand mill manufactured by Kansai Paint Co., Ltd., and stirred at a rotational speed of 1200 rpm for 30 minutes to prepare a resin coating layer forming solution having a solid content of 11% by weight.

(Carrier 1)
Place 2000 parts by weight of carrier core material 1 in a vacuum degassing type 5 L kneader, and further add 180 parts by weight of the resin coating layer forming solution. While stirring, reduce the pressure to −200 mmHg at 80 ° C. and mix for 80 minutes. The temperature was reduced, and the mixture was stirred and dried at 98 ° C. and −720 mmHg for 20 minutes to obtain primary coated particles. Subsequently, 350 parts by weight of a solution for forming a resin coating layer was added, and the temperature was increased and the pressure was reduced, followed by stirring and drying at 98 ° C. and −720 mmHg for 30 minutes to obtain coated particles. Next, sieving was performed with a 75 μm mesh sieving net to obtain Carrier 1. The SF1 of the carrier 1 was 116, the number of exposed carrier core materials was 20, and the ratio of exposed carrier core materials (ferret horizontal diameter of 1 μm to 3 μm) was 90%.

(Carrier 2)
Carrier 2 was obtained in the same manner except that the amount of the resin coating layer forming solution to be added in the second time was changed to 280 parts by weight. The SF1 of the carrier 2 was 116, the number of exposed carrier core materials was 20, and the ratio of exposed carrier core materials (ferret horizontal diameter of 1 μm to 3 μm) was 85%.

(Carrier 3)
Carrier 3 was obtained in the same manner except that carrier core 1 was changed to carrier core 2 with carrier 1. The SF1 of the carrier 3 was 116, the number of exposed carrier core materials was 40, and the ratio of exposed carrier core materials (ferret horizontal diameter of 1 μm to 3 μm) was 90%.

(Carrier 4)
After charging 1000 parts by weight of the carrier core material 3 into a composite fluidized bed coating apparatus MP01-SFP (manufactured by POWREC) and diluting the resin coating layer forming solution twice with toluene, a screen mesh of 0.5 mm, a rotating impeller of 1000 rpm, The coating was performed for 60 minutes under the conditions of a discharge rate of 1.2 m ³ / min, a coating speed of 2.5 g / min, and a temperature of 80 ° C. Next, the coating speed is changed to 5 g / min, and the number of exposed carrier core materials and the ratio of exposed carrier core materials (ferret horizontal diameter is 1 μm or more and 3 μm or less) are confirmed while sampling is performed every 10 minutes. Coating was terminated when the number of exposures was 40 and the ratio of exposed carrier core material (ferret horizontal diameter of 1 μm to 3 μm) reached 90%. The additional coating time was 15 minutes. After taking out, the carrier 4 was obtained by sieving with a sieving mesh of 75 μm mesh. The SF1 of the carrier 4 was 125, the number of exposed carrier core materials was 40, and the ratio of exposed carrier core materials (ferret horizontal diameter of 1 μm to 3 μm) was 90%.

(Carrier 5)
A carrier 5 was obtained in the same manner except that the carrier core material 1 was changed to the carrier core material 4 with the carrier 1. The SF1 of the carrier 5 was 140, the number of exposed carrier core materials was 20, and the ratio of exposed carrier core materials (ferret horizontal diameter of 1 μm to 3 μm) was 90%.

(Carrier 6)
Carrier 6 was obtained in the same manner as carrier 4 except that carrier core material 3 was changed to carrier core material 1 and the additional coating time was 80 minutes. The SF1 of the carrier 6 was 116, and the number of exposed carrier core materials was zero.

(Carrier 7)
Carrier 7 was obtained in the same manner except that the amount of the resin coating layer forming solution to be added second time was 210 parts by weight with carrier 1. The SF1 of the carrier 7 was 116, the number of exposed carrier core materials was 20, and the ratio of exposed carrier core materials (ferret horizontal diameter of 1 μm to 3 μm) was 50%.

(Carrier 8)
After 1000 parts by weight of the carrier core material 1 is put into a vacuum degassing type 5L kneader, and further 100 parts by weight of the solution for forming the resin coating layer is added, the mixture is stirred for 80 minutes at 80 ° C. while reducing the pressure to −780 mmHg. The temperature was raised, and the mixture was stirred and dried at 98 ° C. for 20 minutes to obtain primary coated particles. Subsequently, 350 parts by weight of a solution for forming a resin coating layer was added, and the temperature was increased and the pressure was reduced, followed by stirring and drying at 98 ° C. and −720 mmHg for 30 minutes to obtain coated particles. Next, sieving was carried out using a 75 μm mesh sieving net to obtain a carrier 8. The SF1 of the carrier 8 was 116, the number of exposed carrier core materials was 10, and the ratio of exposed carrier core materials (ferret horizontal diameter of 1 μm to 3 μm) was 90%.

(Carrier 9)
In the production of the carrier 4, the carrier 9 was obtained in the same manner except that the carrier core material 1 was used, the rotary impeller was 1200 rpm, and the coating speed was 2.7 g / min. SF1 of the carrier 9 was 116, the number of exposed carrier core materials was 60, and the ratio of exposed carrier core materials (ferret horizontal diameter of 1 μm to 3 μm) was 90%.

(Carrier 10)
In the production of carrier 1, carrier 10 was obtained in the same manner except that the resin coating layer forming solution to be added second time was changed to 300 parts by weight. SF1 of the carrier 10 was 116, the number of exposed carrier core materials was 20, and the ratio of exposed carrier core materials (ferret horizontal diameter of 1 μm to 3 μm) was 80%.

(Carrier 11)
In the production of the carrier 5, the carrier 11 was obtained in the same manner except that 330 parts by weight of the resin coating layer forming solution to be put in the second time and the stirring time at the time of drying were set to 60 minutes. SF1 of the carrier 11 was 130, the number of exposed carrier core materials was 20, and the ratio of exposed carrier core materials (ferret horizontal diameter of 1 μm to 3 μm) was 90%.

(Carrier 12)
After adding 2000 parts by weight of the carrier core material 1 to a vacuum degassing type 5 L kneader, and further adding 100 parts by weight of the resin coating layer forming solution, stirring the mixture at 80 ° C. to −780 mmHg and mixing for 20 minutes, The temperature was raised, and the mixture was stirred and dried at 98 ° C. for 30 minutes to obtain primary coated particles. Subsequently, 630 parts by weight of the resin coating layer forming solution was added, the temperature was increased and the pressure was reduced, and the mixture was stirred and dried at 98 ° C. and −720 mmHg for 40 minutes to obtain coated particles. Next, sieving was performed with a 75 μm mesh sieving mesh to obtain a carrier 12. The SF1 of the carrier 12 was 116, the number of exposed carrier core materials was 5, and the ratio of exposed carrier core materials (ferret horizontal diameter of 1 μm to 3 μm) was 90%.

(Carrier 13)
In the production of carrier 1, carrier 13 was obtained in the same manner except that the resin coating layer forming solution to be added second time was changed to 150 parts by weight. The SF1 of the carrier 13 was 116, the number of exposed carrier core materials was 65, and the ratio of exposed carrier core materials (ferret horizontal diameter of 1 μm to 3 μm) was 90%.

(Carrier 14)
A carrier 14 was obtained in the same manner except that the carrier core material 5 was used in the production of the carrier 1. SF1 of the carrier 14 was 116, the number of exposed carrier core materials was 20, and the ratio of exposed carrier core materials (ferret horizontal diameter of 1 μm to 3 μm) was 75%.

(Preparation of resin dispersion 1)
Ethylene glycol (Wako Pure Chemical Industries, Ltd.) 37 parts by weight Neopentyl glycol (Wako Pure Chemical Industries, Ltd.) 65 parts by weight 1,9-nonanediol (Wako Pure Chemical Industries, Ltd.) 32 parts by weight 96 parts by weight of terephthalic acid (manufactured by Wako Pure Chemical Industries, Ltd.) The above monomer was charged into a flask and heated to 200 ° C. over 1 hour. After confirming that the reaction system was uniformly stirred, dibutyl 1.2 parts by weight of tin oxide was added. Further, while distilling off the generated water, the temperature was increased from the same temperature to 240 ° C. over 6 hours, and the dehydration condensation reaction was continued at 240 ° C. for another 4 hours. The acid value was 9.4 mgKOH / g, and the weight average molecular weight. A polyester resin having 13,000 and a glass transition point of 62 ° C. was obtained.

Subsequently, this was transferred in a molten state to Cavitron CD1010 (manufactured by Eurotech Co., Ltd.) at a rate of 100 g / min. A 0.37 wt% diluted ammonia water obtained by diluting reagent ammonia water with ion-exchanged water is placed in a separately prepared aqueous medium tank and heated at 120 ° C. with a heat exchanger at a rate of 0.1 liter per minute. Simultaneously with the polyester resin melt, it was transferred to the Cavitron. A Cavitron is operated under conditions of a rotor rotation speed of 60 Hz and a pressure of 5 kg / cm ² , a resin having a volume average particle size of 160 nm, a solid content of 30% by weight, a glass transition point of 62 ° C., and a weight average molecular weight Mw of 13,000. Dispersion 1 was obtained.

(Preparation of colorant dispersion)
Cyan pigment (CI Pigment Blue 15: 3, manufactured by Dainichi Seika Kogyo Co., Ltd.) 10 parts by weight Anionic surfactant (Neogen SC, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 2 parts by weight Ion-exchanged water 80 Part by weight The above components were mixed and dispersed for 1 hour with a high-pressure impact disperser Ultimateizer (HJP30006, manufactured by Sugino Machine Co., Ltd.) to obtain a colorant dispersion having a volume average particle size of 180 nm and a solid content of 20%. .

(Preparation of binder resin 2)
Decanedioic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) 81 parts by weight Hexanediol (manufactured by Wako Pure Chemical Industries, Ltd.) 47 parts by weight The above monomer was charged into a flask and heated to 160 ° C. over 1 hour. Was confirmed to be uniformly stirred, and 0.03 part by weight of dibutyltin oxide was added. Further, while distilling off the water produced, the temperature was raised from the same temperature to 200 ° C. over 6 hours, and the dehydration condensation reaction was continued at 200 ° C. for another 4 hours to complete the reaction. After cooling the reaction solution, the solid obtained by solid-liquid separation was dried at 40 ° C. under vacuum to obtain a crystalline binder resin 2.

  The melting point of the obtained binder resin 2 was 64 ° C. as a result of measurement using a differential thermal scanning calorimeter DSC-7 manufactured by Perkinelmer. The weight average molecular weight was 15,000 when measured using tetrahydroxyfuran (THF) as a solvent using a molecular weight measuring device HLC-8020 manufactured by Tosoh Corporation.

(Adjustment of resin dispersion 2)
Binder resin 2 50 parts by weight Anionic surfactant (Neogen SC, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 2 parts by weight Ion-exchanged water 200 parts by weight The above components are heated to 120 ° C. After sufficiently dispersing at T50, the mixture was dispersed with a pressure discharge type homogenizer, and collected when the volume average particle diameter reached 180 nm. Thus, a resin dispersion 2 having a solid content of 20% by weight was obtained.

(Preparation of release agent dispersion)
Paraffin wax (HNP-9, manufactured by Nippon Seiki Co., Ltd.) 50 parts by weight Anionic surfactant (Neogen SC, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 2 parts by weight Ion-exchanged water 200 parts by weight And then sufficiently dispersed with IKE Ultra Turrax T50, and then dispersed with a pressure discharge homogenizer to obtain a release agent particle dispersion having a volume average particle size of 200 nm and a solid content of 20%.

(Toner 1)
Resin dispersion 1 150 parts by weight Colorant dispersion 25 parts by weight Release agent dispersion 35 parts by weight Resin dispersion 2 50 parts by weight Polyaluminum chloride 0.4 parts by weight Ion exchange water 100 parts by weight After thoroughly mixing and dispersing using IKE's Ultra Turrax T50 in the flask made, the flask was heated to 48 ° C. with stirring in an oil bath for heating. After maintaining at 48 ° C. for 60 minutes, 70 parts by weight of the same resin dispersion 1 as above was gradually added thereto.

  Then, after adjusting the pH in the system to 8.0 using a sodium hydroxide aqueous solution having a concentration of 0.5 mol / L, the stainless steel flask is sealed, and the stirring shaft seal is magnetically sealed while stirring is continued. Heated to 90 ° C. and held for 30 minutes. After completion of the reaction, the temperature was lowered at a rate of 5 ° C./min, filtered and thoroughly washed with ion-exchanged water, followed by solid-liquid separation by Nutsche suction filtration. This was further redispersed using 3 L of ion exchange water at 30 ° C., and stirred and washed at 300 rpm for 15 minutes. This washing operation was further repeated 6 times, and when the pH of the filtrate became 7.54 and the electric conductivity was 6.5 μS / cm, No. was obtained by Nutsche suction filtration. Solid-liquid separation was performed using 5A filter paper. Next, vacuum drying was continued for 24 hours to obtain toner particles 1.

The volume average particle diameter D50v of the toner particles 1 is 5.7 μm as measured with a Coulter counter, and the volume average particle size distribution index GSDv is 1.20. Further, silica particles (SiO ₂ ) having a primary particle volume average particle size of 40 nm, surface-hydrophobized with hexamethyldisilazane (hereinafter sometimes abbreviated as “HMDS”), metatitanic acid and isobutyl are added to the toner particles 1. Metatitanic acid compound particles having a primary particle volume average particle diameter of 20 nm, which is a reaction product of trimethoxysilane, are added so that the coverage of the surface of each colored particle is 40%, mixed with a Henschel mixer, and statically mixed. Toner 1 for charge image development was produced.

<Example 1>
(Developer 1)
The developer 1 was prepared by mixing the carrier 1 so that the toner 1 was 8% by weight.

(Evaluation)
A DocuCentreColor400 remodeling machine manufactured by Fuji Xerox (specifically, a cleaning blade in contact with the photoreceptor was changed to a polyurethane rebound resilience of 65%) was further remodeled so that the printing speed could be arbitrarily changed. The modified machine was then placed in an environment of 30 ° C. and 88% RH. Using this modified machine, Developer 1 was set to 1/10 of the standard printing speed, and A4 full surface printing was performed 10 sheets at 50% Cin. Subsequently, the printing speed was set to 1.8 times the standard, and 10 sheets of A4 full surface printing were similarly performed at 50% Cin. This was defined as one cycle and repeated 500 cycles. At this time, the fixing device was removed, and only transfer from development to paper was performed. Thereafter, a fixing device was attached, the printing speed was set as a standard, solid printing was performed on a band having a width of 10 cm, and 3 sheets of A4 full surface Cin 30% printing were each performed. Evaluation was made according to the following criteria. The results are shown in Table 1.

[Striped image defects]
◎: Not confirmed ○: Although thin streaks can be seen, there is no problem in practical use △: 5 to 10 streaks are confirmed on a 10 cm wide belt Solid ×: 10 or more streaks on a 10 cm solid belt Is confirmed
[Cin 30% image]
A: There is no disturbance in the image B: Several thin spots are confirmed, but there is no problem in practical use. A: One or more white spots are confirmed X: Four or more white spots are confirmed Ru

(Example 2)
In Example 1, it carried out similarly except changing the carrier 1 to the carrier 2. The results are shown in Table 1.

(Example 3)
In Example 1, it carried out similarly except changing the carrier 1 to the carrier 3. The results are shown in Table 1.

Example 4
In Example 1, it carried out similarly except changing the carrier 1 to the carrier 4. The results are shown in Table 1.

(Example 5)
In Example 1, the same operation was performed except that the cleaning blade was replaced with a blade having a rebound resilience of 55%. The results are shown in Table 1.

(Example 6)
In Example 1, it carried out similarly except having changed the carrier 1 to the carrier 8. The results are shown in Table 1.

(Example 7)
In Example 1, it carried out similarly except changing the carrier 1 to the carrier 9. The results are shown in Table 1.

(Example 8)
In Example 1, it carried out similarly except changing the carrier 1 to the carrier 10. The results are shown in Table 1.

Example 9
In Example 1, the same operation was performed except that the cleaning blade was replaced with a blade having a rebound resilience of 60%. The results are shown in Table 1.

(Example 10)
In Example 1, the same procedure was followed except that the cleaning blade was replaced with a blade with 75% impact resilience. The results are shown in Table 1.

(Example 11)
The same procedure as in Example 1 was performed except that the cleaning blade was replaced with a blade having a rebound resilience of 80%. The results are shown in Table 1.

(Comparative Example 1)
In Example 1, it carried out similarly except changing the carrier 1 to the carrier 5. The results are shown in Table 1.

(Comparative Example 2)
In Example 1, it carried out similarly except changing the carrier 1 to the carrier 6. The results are shown in Table 1.

(Comparative Example 3)
In Example 1, it carried out similarly except changing the carrier 1 to the carrier 7. The results are shown in Table 1.

(Comparative Example 4)
In Comparative Example 2, the same procedure was performed except that the cleaning blade was replaced with a blade having a rebound resilience of 55%. The results are shown in Table 1.

(Comparative Example 5)
In Example 1, it carried out similarly except changing the carrier 1 to the carrier 11. The results are shown in Table 1.

(Comparative Example 6)
In Example 1, it carried out similarly except changing the carrier 1 to the carrier 12. The results are shown in Table 1.

(Comparative Example 7)
In Example 1, it carried out similarly except having changed the carrier 1 to the carrier 13. FIG. The results are shown in Table 1.

(Comparative Example 8)
In Example 1, the same procedure was performed except that the carrier 1 was replaced with the carrier 14. The results are shown in Table 1.

  As described above, in Examples 1 to 11, even when low-speed printing and high-speed printing were alternately repeated, the occurrence of streak-like image defects was suppressed, and a good image could be obtained.

1 is a schematic diagram illustrating an example of an image forming apparatus according to an embodiment of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Image forming apparatus, 10 charging part, 12 exposure part, 14 electrophotographic photosensitive member, 16 developing part, 18 transfer part, 20 cleaning part, 22 fixing part, 24 to-be-transferred body.

Claims (3)

Including a carrier core material and a resin coating layer,
The shape factor SF1 of the carrier is 125 or less,
The number of exposure of the carrier core material on the carrier surface is 10 or more and 60 or less,
A carrier for developing an electrostatic charge image, characterized in that 80% by number or more of the exposed carrier core material having a ferret horizontal diameter in the range of 1 μm to 3 μm.   An electrostatic charge image developing developer comprising the electrostatic charge image developing carrier according to claim 1 and an electrostatic charge image developing toner. An image carrier, a latent image forming unit that forms an electrostatic latent image on the surface of the image carrier, a developing unit that develops the electrostatic latent image using a developer to form a toner image, and the development A transfer unit that transfers the toner image to the transfer target, a cleaning unit that removes a residue remaining on the surface of the image carrier,
Have
The developer is an electrostatic charge image developing developer according to claim 2,
The image forming apparatus, wherein the cleaning unit includes an elastic blade, and the resilience of the elastic blade is not less than 60% and not more than 75%.

Images