JP2018116093A - Carrier, two-component developer using the same, developer for supply, image formation apparatus, process cartridge and image formation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carrier which achieves high image quality and high durability even under high temperature and high humidity.SOLUTION: A carrier includes a core and a coating layer which coats the core. The coating layer includes electric conductive fine particles. The electric conductive fine particles include tungsten-doped tin oxide subjected to surface processing.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a carrier, a two-component developer using the carrier, a replenishment developer, an image forming apparatus, a process cartridge, and an image forming method.

  In electrophotographic image formation, an electrostatic latent image is formed on an electrostatic latent image carrier such as a photoconductive substance, and a charged toner is attached to the electrostatic latent image to form a toner image. After that, the toner image is transferred to a recording medium and fixed to form an output image. In recent years, the technology of copying machines and printers using an electrophotographic system is rapidly expanding from monochrome to full color, and the full color market tends to expand.

  In full-color image formation, generally, color toners of three colors of yellow, magenta, and cyan or four color toners obtained by adding black to this are laminated to reproduce all colors. Therefore, in order to obtain a clear full color image with excellent color reproducibility, it is necessary to smooth the surface of the fixed toner image to reduce light scattering. For these reasons, the image gloss of conventional full-color copying machines and the like is often 10 to 50% of medium to high gloss.

  In general, as a method for fixing a dry toner image on a recording medium, a contact heating fixing method in which a roller or belt having a smooth surface is heated and pressed against the toner is frequently used. Such a method has high thermal efficiency and enables high-speed fixing, and can give gloss and transparency to a color toner image. On the other hand, the surface of the heat fixing member and the molten toner are brought into contact with each other under pressure. Since the toner image is peeled off, a so-called offset phenomenon occurs in which a part of the toner image adheres to the surface of the fixing roller and is transferred onto another image.

  In order to prevent such an offset phenomenon, the surface of the fixing roller is formed of silicone rubber or fluorine resin having excellent releasability, and further, an oil for preventing toner adhesion such as silicone oil is applied to the surface of the fixing roller. This method is generally adopted. However, such a method is extremely effective in preventing toner offset, but requires a device for supplying oil, and there is a problem that the fixing device is increased in size.

  For this reason, in monochrome image formation, an oilless system in which viscoelasticity at the time of melting is large and toner containing a release agent is used so that the melted toner does not break internally, so that no oil is applied to the fixing roller, or There is a tendency to adopt a system in which a small amount of oil is applied.

  On the other hand, in full-color image formation, as in the case of monochrome image formation, an oilless system tends to be employed for the purpose of downsizing the fixing device and simplifying the configuration. However, in full-color image formation, it is necessary to reduce the viscoelasticity of the toner at the time of melting in order to smooth the surface of the fixed toner image. Therefore, offset occurs more than in the case of monochrome image formation without gloss. This makes it difficult to adopt an oilless system. Further, when a toner containing a release agent is used, adhesion of the toner is increased and transferability to a recording medium is decreased. Furthermore, there is a problem in that the durability is lowered due to the occurrence of toner filming and a decrease in chargeability.

  On the other hand, as a carrier, prevention of toner filming, formation of a uniform surface, prevention of surface oxidation, prevention of decrease in moisture sensitivity, extension of developer life, prevention of adhesion to the surface of a photoreceptor, photosensitivity For the purpose of protecting the body from scratches or abrasion, controlling the charge polarity, adjusting the charge amount, etc., the carrier core material surface is coated with a resin having a low surface energy, such as a fluororesin or a silicone resin. Long life has been achieved.

  Examples of a carrier coated with a low surface energy resin include a carrier coated with a room temperature curable silicone resin and a positively chargeable nitrogen resin described in JP-A No. 55-127469 of Patent Document 1, A carrier coated with a coating material containing at least one modified silicone resin described in JP-A-55-157751; a room temperature-curable silicone resin described in JP-A-56-140358 of Patent Document 3; and a styrene / acrylic resin A carrier having a coated resin coating layer, a carrier in which the core particle surface described in Japanese Patent Application Laid-Open No. 57-96355 of Patent Document 4 is coated with two or more layers of silicone resin so that there is no adhesion between the layers, Patent Document 5 JP-A-57-96356 discloses a carrier in which a silicone resin is coated on the surface of a core particle, and JP-A-57-96356 discloses A carrier whose surface is coated with a silicon resin containing silicon carbide described in Japanese Patent Application Laid-Open No. 8-207054, Examples thereof include a chargeable carrier, a carrier coated with a coating material containing a fluorine alkyl acrylate described in JP-A-62-273576 of Patent Document 8, and a developer comprising a toner containing a chromium-containing azo dye. .

  However, in recent years, carriers have long lifespan, and image forming devices are used everywhere in the world to provide stable images in a wide range of environments from high temperature and high humidity to low temperature and low humidity. Is required. In particular, at high temperature and high humidity, the carrier charge amount fluctuation and resistance fluctuation increase, and it is difficult to maintain image quality. This is because the amount of moisture in the air increases, chemical and physical adsorption to the carrier proceeds, and the carrier quality changes.

  Examples of carriers that provide stable images under high temperature and high humidity include, for example, Japanese Patent Application Laid-Open No. 2001-343790 of Patent Document 9, Japanese Patent Application Laid-Open No. 2007-17838 of Patent Document 10, and Japanese Patent Application Laid-Open No. 2015 of Patent Document 11. 179258 and the like. However, these Patent Documents 8 to 10 all relate to the charge amount fluctuation due to moisture adsorption of the carrier, and there is no disclosure regarding the carrier resistance fluctuation in the prior art, and there is room for improvement.

  An object of the present invention is to provide a carrier that enables high image quality and high durability even under high temperature and high humidity.

The above problem is solved by the following configuration 1).
1) A carrier having a core and a coating layer covering the core,
The coating layer includes conductive fine particles,
The carrier, wherein the conductive fine particles include tungsten-doped tin oxide subjected to a surface treatment.

  According to the present invention, it is possible to provide a carrier that enables high image quality and high durability even under high temperature and high humidity.

It is a figure explaining the cell for measuring volume specific resistance in the present invention. It is a figure which shows an example of the process cartridge of this invention.

Hereinafter, embodiments of the present invention will be described in detail.
The carrier of the present invention includes a core and a coating layer that covers the core, the coating layer includes conductive fine particles, and the conductive fine particles include tungsten-doped tin oxide subjected to surface treatment. Features.

In the prior art, there are conductive fine particles in which a conductive material is coated on a core of metal or the like. However, such conductive fine particles have a large particle size and further have a toner spent due to high hardness. It is easy to proceed and is not preferable.
On the other hand, according to the study by the present inventor, tungsten-doped tin oxide has a low powder specific resistance, no contamination to toner even when used in a color developer, and easy control of the primary particle size. It has been found to have characteristics such as being. In the present invention, by using this tungsten-doped tin oxide, the resistance is stable over a long period of time even under high temperature and high humidity, the toner spent is suppressed, the charging stability is excellent, the image quality is high, and the durability is enhanced. A carrier that enables it can be provided.

  The tungsten-doped tin oxide in the present invention is subjected to a surface treatment. Since tungsten-doped tin oxide tends to aggregate, surface treatment is required to improve dispersibility. By performing the surface treatment, chemical moisture adsorption at a portion exposed to the carrier surface under high temperature and high humidity is suppressed. Further, the surface treatment is performed to increase dispersibility, so that tungsten-doped tin oxide is uniformly present in the coating layer. Then, the unevenness derived from the conductive fine particles on the carrier surface is reduced, the carrier specific surface area is reduced, and physical water adsorption under high temperature and high humidity can be suppressed. For the above reasons, the carrier resistance fluctuation due to moisture adsorption can be suppressed even under high temperature and high humidity, and a stable image can be output.

  In the surface treatment of tungsten-doped tin oxide in the present invention, various known surface treatment agents can be used as long as the above effects can be achieved. Suitable surface treatment agents include silane coupling agents such as amino silane coupling agents, methacryloxy silane coupling agents, vinyl silane coupling agents, mercapto silane coupling agents, and alkyl silane cups. Examples thereof include a ring agent and a styryl silane coupling agent.

  The adhesion amount of the surface treatment agent is, for example, 0.1 to 10% by mass, preferably 1 to 5% by mass with respect to the tungsten-doped tin oxide. The surface treatment can be performed with a known stirring device.

The primary particle size of tungsten-doped tin oxide is preferably 50 nm to 300 nm, and preferably 100 nm to 250 nm. When the conductive fine particles are 50 nm or more, the dispersibility is improved, and it is difficult to be present in the coating layer in an aggregated state, the specific surface area of the carrier is reduced, and physical moisture adsorption can be suppressed. In addition, when the thickness is 300 nm or less, there is no agitation hazard in the developing machine, and a decrease in resistance due to abrasion of the coating layer and a decrease in charge amount due to the progress of toner spent can be avoided.
The primary particle size of tungsten-doped tin oxide can be measured using, for example, Nanotrack UPA-EX150 (manufactured by Nikkiso Co., Ltd.), and the primary particle size of the present invention is an average primary particle size.

A smaller powder specific resistance of tungsten-doped tin oxide is preferable because the ability to adjust the resistance of the carrier can be achieved with a small amount of addition. The powder specific resistance of tungsten-doped tin oxide is preferably 20 Ω · cm or less. When the specific resistance of the powder is 20 Ω · cm or less, the amount used for adjusting the resistance of the carrier can be reduced, the unevenness of the coating layer and the formation of a strong coating layer can be suppressed, and the toner spent and charge reduction Can be prevented.
The powder specific resistance can be measured using, for example, an LCR meter AR-480D type (manufactured by Keisei).

  In the present invention, the conductive fine particles are preferably composed of tungsten-doped tin oxide as described above. However, if necessary, other conductive fine particles may be added in an amount of 50% by mass or less with respect to the entire conductive fine particles. It can also be used in a range. The primary particle size of the other conductive fine particles is preferably within the primary particle size range of the tungsten-doped tin oxide.

  Content of tungsten dope tin oxide is 20-60 mass% with respect to the whole coating layer, for example, Preferably it is 30-50 mass%.

The carrier of the present invention preferably has a volume average particle size of 32 μm or more and 40 μm or less. When the volume average particle diameter of the carrier is 32 μm or more, carrier adhesion can be prevented, and when it is 40 μm or less, reproducibility of image details is improved and a fine image can be formed.
The volume average particle diameter can be measured using, for example, a Microtrac particle size distribution model HRA9320-X100 (manufactured by Nikkiso Co., Ltd.).

  The carrier of the present invention preferably has a volume resistivity of 10 to 14 (Log Ω · cm). When the volume resistivity is 10 (Log Ω · cm) or more, carrier adhesion in the non-image area can be prevented, and when the volume resistivity is 14 (Log Ω · cm) or less, the edge effect becomes an acceptable level.

  The volume resistivity can be measured using the cell shown in FIG. Specifically, first, an electrode (1a) and an electrode (1b) having a surface area of 2.5 cm × 4 cm are placed in a cell made of a fluororesin container (2) containing a distance of 0.2 cm, and a carrier (3 ) And is tapped 10 times with a drop height of 1 cm and a tapping speed of 30 times / minute. Next, a 1000 V DC voltage was applied between the electrodes (1a) and (1b), and a resistance value r [Ω] after 30 seconds was measured using a high resistance meter 4329A (manufactured by Yokogawa Hewlett-Packard Company). From the following formula 2, the volume resistivity [Ω · cm] can be calculated.

  The coating layer of the carrier can contain a resin. As the resin, a silicone resin, an acrylic resin, or a combination thereof can be used. Acrylic resin has excellent adhesion properties and low brittleness, so it has very high wear resistance. However, its surface energy is high, so if it is used in combination with easily spent toner, toner component spent will accumulate. In some cases, this causes problems such as a decrease in charge amount. In this case, this problem can be solved by using together a silicone resin that has an effect that it is difficult to spend the toner component due to the low surface energy and the accumulation of the spent component is difficult to progress due to film scraping. In addition, since the silicone resin has weak adhesiveness and high brittleness, it also has a weak point that it has poor wear resistance. Therefore, it is preferable to use these two types of resins in a balanced manner. For example, the silicone resin is preferably added in an amount of 10 to 80% by mass, and the acrylic resin is preferably added in an amount of 5 to 30% by mass.

  As used herein, the term “silicone resin” refers to all commonly known silicone resins, including straight silicone consisting only of organosilosan bonds, silicone resins modified with alkyd, polyester, epoxy, acrylic, urethane, etc. However, it is not limited to this. Examples of commercially available straight silicone resins include KR271, KR255, and KR152 manufactured by Shin-Etsu Chemical, SR2400, SR2406, and SR2410 manufactured by Toray Dow Corning Silicone. In this case, it is possible to use the silicone resin alone, but it is also possible to simultaneously use other components that undergo a crosslinking reaction, charge amount adjusting components, and the like. Further, modified silicone resins include KR206 (alkyd modified), KR5208 (acrylic modified), ES1001N (epoxy modified), KR305 (urethane modified) manufactured by Shin-Etsu Chemical, SR2115 (epoxy modified) manufactured by Toray Dow Corning Silicone. , SR2110 (alkyd modified) and the like.

  Moreover, you may use the acrylic copolymer which consists of monomers A, B, and C as shown to the following general formula (1)-(3) as resin used for a coating layer. The copolymer is extremely tough and difficult to scrape, and can be highly durable. Even when the coating layer is thin, the core is difficult to be exposed by use.

In the general formulas (1) to (3), R ¹ represents a hydrogen atom or a methyl group, R ² represents an alkyl group having 1 to 4 carbon atoms, and R ³ represents an alkyl group having 1 to 8 carbon atoms. Alternatively, it represents an alkoxy group having 1 to 4 carbon atoms, m represents an integer of 1 to 8, X represents 10 mol% to 40 mol%, Y represents 10 mol% to 40 mol%, and Z represents 30 mol% to 80 mol%. Represents. And it is 60 mol% <Y + Z <90 mol%.

  As the polycondensation catalyst used for the preparation of the acrylic copolymer, a titanium-based catalyst, a tin-based catalyst, a zirconium-based catalyst, and an aluminum-based catalyst are mentioned. In the present invention, among these various catalysts, excellent results are obtained. Among the titanium-based catalysts, titanium diisopropoxybis (ethyl acetoacetate) is most preferable as the catalyst. This is considered to be because the effect of promoting the condensation reaction of the silanol group is large and the catalyst is hardly deactivated.

  The acrylic resin referred to in this specification refers to all resins having an acrylic component, and is not particularly limited. In addition, it is possible to use the acrylic resin alone, but it is also possible to use at least one other component that undergoes a crosslinking reaction at the same time. Examples of other components that undergo a crosslinking reaction include amino resins and acidic catalysts, but are not limited thereto. The amino resin here refers to guanamine, melamine resin and the like, but is not limited thereto. Moreover, what has a catalytic action can be used with an acidic catalyst here. For example, it has a reactive group such as a fully alkylated type, a methylol group type, an imino group type, and a methylol / imino group type, but is not limited thereto.

The coating layer further preferably contains a cross-linked product of an acrylic resin and an amino resin.
Thereby, fusion | melting of coating layers can be suppressed, maintaining moderate elasticity.
The amino resin is not particularly limited, but a melamine resin and a benzoguanamine resin are preferable because the charge imparting ability of the carrier can be improved. Further, when it is necessary to appropriately control the charge imparting ability of the carrier, another amino resin may be used in combination with the melamine resin and / or benzoguanamine resin.

  As the acrylic resin capable of crosslinking with the amino resin, those having a hydroxyl group and / or a carboxyl group are preferable, and those having a hydroxyl group are more preferable. Thereby, adhesiveness with core material particle | grains or electroconductive fine particles can further be improved, and the dispersion stability of electroconductive fine particles can also be improved. In this case, the acrylic resin preferably has a hydroxyl value of 10 mgKOH / g or more, and more preferably 20 mgKOH / g or more.

In the present invention, the composition for forming the coating layer preferably contains a silane coupling agent.
Thereby, electroconductive fine particles can be disperse | distributed stably.
The silane coupling agent is not particularly limited, but r- (2-aminoethyl) aminopropyltrimethoxysilane, r- (2-aminoethyl) aminopropylmethyldimethoxysilane, r-methacryloxypropyltrimethoxysilane, N -Β- (N-vinylbenzylaminoethyl) -r-aminopropyltrimethoxysilane hydrochloride, r-glycidoxypropyltrimethoxysilane, r-mercaptopropyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, Vinyltriacetoxysilane, r-chloropropyltrimethoxysilane, hexamethyldisilazane, r-anilinopropyltrimethoxysilane, vinyltrimethoxysilane, octadecyldimethyl [3- (trimethoxysilyl) propyl] ammonium Chloride, r-chloropropylmethyldimethoxysilane, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, allyltriethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, dimethyldiethoxysilane, 1, Examples include 3-divinyltetramethyldisilazane and methacryloxyethyldimethyl (3-trimethoxysilylpropyl) ammonium chloride, and two or more of them may be used in combination.

  Commercially available silane coupling agents include AY43-059, SR6020, SZ6023, SH6026, SZ6032, SZ6050, AY43-310M, SZ6030, SH6040, AY43-026, AY43-031, sh6062, Z-6911, sz6300, sz6075, sz6079, sz6083, sz6070, sz6072, Z-6721, AY43-004, Z-6187, AY43-021, AY43-043, AY43-040, AY43-047, Z-6265, AY43-204M, AY43-048, Z- 6403, AY43-206M, AY43-206E, Z6341, AY43-210MC, AY43-083, AY43-101, AY43-013, AY43-158E, Z-6920 Z-6940 (Toray Silicone Co., Ltd.).

  When using a silicone resin, it is preferable that the addition amount of a silane coupling agent is 0.1-10 mass% with respect to this silicone resin. When the addition amount of the silane coupling agent is less than 0.1% by mass, the adhesion between the core material particles or conductive fine particles and the silicone resin is lowered, and the coating layer may fall off during long-term use. If it exceeds 10 mass%, toner filming may occur during long-term use.

  The film thickness of the coating layer in this invention is 0.1 micrometer-1.0 micrometer, for example, Preferably it is 0.3 micrometer-0.8 micrometer.

  The core in the carrier of the present invention is not particularly limited as long as it is a magnetic substance, but is not limited to ferromagnetic metals such as iron and cobalt; iron oxides such as magnetite, hematite, and ferrite; various alloys and compounds; Examples thereof include resin particles dispersed therein. Among these, Mn-based ferrite, MnMg-based ferrite, MnMg—Sr ferrite, and the like are preferable in consideration of the environment.

  The volume average particle diameter of the core is not particularly limited, but it is preferably 20 μm or more from the viewpoint of carrier adhesion and carrier scattering prevention, and abnormal image generation such as carrier streaks is prevented and image quality is deteriorated. From the viewpoint of prevention, those having a thickness of 100 μm or less are preferable, and in particular, by using a material having a thickness of 20 to 60 μm, it is possible to more appropriately meet the recent improvement in image quality. The volume average particle diameter can be measured using, for example, a Microtrac particle size distribution model HRA9320-X100 (manufactured by Nikkiso Co., Ltd.).

The two-component developer of the present invention has the carrier and toner of the present invention.
The toner contains a binder resin and a colorant, and may be a monochrome toner or a color toner. Further, the toner particles may contain a release agent in order to be applied to an oilless system in which toner fixing prevention oil is not applied to the fixing roller. Such toner generally tends to cause filming. However, since the carrier of the present invention can suppress filming, the developer of the present invention maintains good quality for a long time. Can do.
Further, color toners, particularly yellow toners, generally have a problem that color stains occur due to scraping of the coating layer of the carrier, but the developer of the present invention can suppress the occurrence of color stains.

  In the two-component developer of the present invention, when the whole is 100 parts by mass, for example, the carrier is preferably used in the range of 88 to 98 parts by mass, and the toner is used in the range of 2 to 12 parts by mass. Is preferred.

  The toner can be produced using a known method such as a pulverization method or a polymerization method. For example, when a toner is manufactured using a pulverization method, first, a melt-kneaded product obtained by kneading a toner material is cooled, pulverized, and classified to prepare base particles. Next, in order to further improve transferability and durability, an external additive is added to the base particles to produce a toner.

  At this time, the apparatus for kneading the toner material is not particularly limited, but a batch type two roll; Banbury mixer; KTK type twin screw extruder (manufactured by Kobe Steel), TEM type twin screw extruder (Toshiba Machine) A continuous twin screw extruder such as a twin screw extruder (manufactured by KCK), a PCM type twin screw extruder (manufactured by Ikegai Iron Works), a KEX type twin screw extruder (manufactured by Kurimoto Iron Works); Examples thereof include a continuous single-shaft kneader such as Ko Nida (manufactured by Buss).

Further, when the cooled melt-kneaded product is pulverized, it is roughly pulverized using a hammer mill, a rotoplex, etc., and then finely pulverized using a fine pulverizer using a jet stream, a mechanical pulverizer or the like. be able to. In addition, it is preferable to grind | pulverize so that an average particle diameter may be set to 3-15 micrometers.
Furthermore, when classifying the crushed melt-kneaded material, a wind classifier or the like can be used. In addition, it is preferable to classify so that the average particle diameter of the base particles is 5 to 20 μm.
In addition, when an external additive is added to the base particle, the external additive adheres to the surface of the base particle while being pulverized by mixing and stirring using a mixer.

The binder resin is not particularly limited, but is a homopolymer of styrene such as polystyrene, poly-p-styrene, polyvinyltoluene and the like; and a styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene. -Vinyltoluene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-methacrylic acid copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer Styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene Copolymer, styrene-isoprene copolymer , Styrene copolymers such as styrene-maleic acid ester copolymer; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polyester, polyurethane, epoxy resin, polyvinyl butyral, polyacryl Examples thereof include acids, rosins, modified rosins, terpene resins, phenol resins, aliphatic or aromatic hydrocarbon resins, and aromatic petroleum resins, and two or more of them may be used in combination.
The binder resin for pressure fixing is not particularly limited, but polyolefins such as low molecular weight polyethylene and low molecular weight polypropylene; ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, styrene-methacrylic acid copolymer. Olefin copolymers such as ethylene-methacrylate copolymer, ethylene-vinyl chloride copolymer, ethylene-vinyl acetate copolymer, ionomer resin; epoxy resin, polyester, styrene-butadiene copolymer, polyvinylpyrrolidone, Examples thereof include methyl vinyl ether-maleic anhydride copolymer, maleic acid-modified phenol resin, phenol-modified terpene resin, and the like, and two or more of them may be used in combination.

  Although it does not specifically limit as a coloring agent (pigment or dye), Cadmium yellow, mineral fast yellow, nickel titanium yellow, Navels yellow, naphthol yellow S, Hansa yellow G, Hansa yellow 10G, benzidine yellow GR, quinoline yellow lake, Yellow pigments such as permanent yellow NCG and tartrazine lake; orange pigments such as molybdenum orange, permanent orange GTR, pyrazolone orange, vulcan orange, indanthrene brilliant orange RK, benzidine orange G, indanthrene brilliant orange GK; bengara, cadmium Red, Permanent Red 4R, Resol Red, Pyrazolone Red, Watching Red Calcium Salt, Lake Red D, Brilliant Kami Red pigments such as 6B, eosin lake, rhodamine lake B, alizarin lake, brilliant carmine 3B; purple pigments such as fast violet B, methyl violet lake; cobalt blue, alkali blue, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, Blue pigments such as phthalocyanine blue partially chlorinated, First Sky Blue, Indanthrene Blue BC; Green pigments such as Chrome Green, Chrome Oxide, Pigment Green B, Malachite Green Lake; Carbon Black, Oil Furnace Black, Channel Black, Lamp Black Azine-based dyes such as acetylene black and aniline black, black pigments such as metal salt azo dyes, metal oxides, and composite metal oxides. It may be.

  The release agent is not particularly limited, but includes polyolefins such as polyethylene and polypropylene, fatty acid metal salts, fatty acid esters, paraffin wax, amide wax, polyhydric alcohol wax, silicone varnish, carnauba wax, ester wax and the like. Two or more kinds may be used in combination.

  The toner may further contain a charge control agent. The charge control agent is not particularly limited, but nigrosine; an azine dye having an alkyl group having 2 to 16 carbon atoms (see Japanese Patent Publication No. 42-1627); I. Basic Yellow 2 (C.I. 41000), C.I. I. Basic Yellow 3, C.I. I. Basic Red 1 (C.I. 45160), C.I. I. Basic Red 9 (C.I. 42500), C.I. I. Basic Violet 1 (C.I. 42535), C.I. I. Basic Violet 3 (C.I. 42555), C.I. I. Basic Violet 10 (C.I. 45170), C.I. I. Basic Violet 14 (C.I. 42510), C.I. I. Basic Blue 1 (C.I. 42025), C.I. I. Basic Blue 3 (C.I. 51005), C.I. I. Basic Blue 5 (C.I. 42140), C.I. I. Basic Blue 7 (C.I. 42595), C.I. I. Basic Blue 9 (C.I. 52015), C.I. I. Basic Blue 24 (C.I. 52030), C.I. I. Basic Blue 25 (C.I. 52025), C.I. I. Basic Blue 26 (C.I. 44045), C.I. I. Basic Green 1 (C.I. 42040), C.I. I. Basic dyes such as Basic Green 4 (C.I. 42000); lake pigments of these basic dyes; I. Solvent Black 8 (C.I. 26150), quaternary ammonium salts such as benzoylmethylhexadecyl ammonium chloride and decyltrimethyl chloride; dialkyltin compounds such as dibutyl and dioctyl; dialkyltin borate compounds; guanidine derivatives; vinyl having an amino group Polyamine resins such as polycondensation polymers and condensation polymers having amino groups; described in JP-B-41-20153, JP-B-43-27596, JP-B-44-6397, and JP-B-45-26478 Metal complex salts of monoazo dyes; salicylic acids described in JP-B-55-42752 and JP-B-59-7385; dialkylsalicylic acid, naphthoic acid, dicarboxylic acid Zn, Al, Co, Cr, Fe, etc. Metal complexes of Examples thereof include honed copper phthalocyanine pigments; organic boron salts; fluorine-containing quaternary ammonium salts; calixarene compounds, and the like. For color toners other than black, white metal salts of salicylic acid derivatives are preferred.

  The external additive is not particularly limited, but inorganic particles such as silica, titanium oxide, alumina, silicon carbide, silicon nitride, boron nitride, etc .; poly having an average particle size of 0.05 to 1 μm obtained by a soap-free emulsion polymerization method Examples thereof include resin particles such as methyl methacrylate particles and polystyrene particles, and two or more kinds may be used in combination. Among these, metal oxide particles such as silica and titanium oxide whose surfaces are hydrophobized are preferable. Furthermore, by using a combination of hydrophobized silica and hydrophobized titanium oxide, the amount of added hydrophobized titanium oxide is higher than that of hydrophobized silica. A toner having excellent charging stability can be obtained.

The replenishment developer of the present invention includes a carrier and a toner, and the carrier is the carrier of the present invention.
By applying the replenishment developer of the present invention to an image forming apparatus that forms an image while discharging excess developer in the developing device, stable image quality can be obtained over a very long period of time. That is, the deteriorated carrier in the developing device and the non-deteriorated carrier in the replenishing developer are replaced, and the charge amount is kept stable over a long period of time, so that a stable image can be obtained. This method is particularly effective when printing a large image area. When printing a large image area, carrier charge deterioration due to toner spent on the carrier is the main carrier deterioration. However, when this method is used, the carrier replenishment amount increases when the image area is large, and the deteriorated carrier is replaced. Increases frequency. Thereby, a stable image can be obtained for an extremely long period of time.
The mixing ratio of the replenishment developer is preferably 2 to 50 parts by mass of toner with respect to 1 part by mass of the carrier. When the amount of toner is less than 2 parts by mass, the amount of replenishment carrier is excessive, the carrier is excessively supplied, and the carrier concentration in the developing device becomes too high, so that the charge amount of the developer tends to increase. Further, when the developer charge amount increases, the developing ability decreases and the image density decreases. On the other hand, if the amount exceeds 50 parts by mass, the carrier ratio in the replenishment developer decreases, so that the replacement of carriers in the image forming apparatus decreases, and the effect on carrier deterioration cannot be expected.

The image forming apparatus of the present invention includes an electrostatic latent image carrier, a charging unit that charges the electrostatic latent image carrier, an exposure unit that forms an electrostatic latent image on the electrostatic latent image carrier, Developing means for developing the electrostatic latent image formed on the electrostatic latent image carrier using the two-component developer of the present invention to form a toner image, and formed on the electrostatic latent image carrier. Transfer means for transferring the toner image to a recording medium, and fixing means for fixing the toner image transferred to the recording medium.
The image forming method of the present invention includes a step of forming an electrostatic latent image on an electrostatic latent image carrier, and the two-component development of the present invention using the electrostatic latent image formed on the electrostatic latent image carrier. Developing with a developer to form a toner image, transferring the toner image formed on the electrostatic latent image carrier to a recording medium, and fixing the toner image transferred to the recording medium Process.
Note that the configuration of the image forming apparatus and method used in the present invention is not limited to the above-described embodiment, and an image forming apparatus and method having other configurations can be used as long as they have similar functions. It is also possible to adopt.

  FIG. 2 shows an example of the process cartridge of the present invention. The process cartridge (10) includes a photoreceptor (11) as an electrostatic latent image carrier, a charging device (12) for charging the photoreceptor (11), and an electrostatic latent image formed on the photoreceptor (11). The toner image formed on the photoconductor (11) and the developing device (13) that develops using the developer of the present invention to form a toner image is transferred to a recording medium and then remains on the photoconductor (11). The cleaning device (14) for removing the toner is integrally supported, and the process cartridge (10) is detachable from the main body of an image forming apparatus such as a copying machine or a printer.

  Hereinafter, a method for forming an image using the image forming apparatus equipped with the process cartridge (10) will be described. First, the photosensitive member (11) is rotationally driven at a predetermined peripheral speed, and the charging device (12) uniformly charges the peripheral surface of the photosensitive member (11) to a predetermined positive or negative potential. Next, exposure light is irradiated onto the peripheral surface of the photoreceptor (11) from an exposure apparatus (not shown) such as a slit exposure type exposure apparatus or an exposure apparatus that performs scanning exposure with a laser beam, and electrostatic latent images are sequentially formed. The Further, the electrostatic latent image formed on the peripheral surface of the photoconductor (11) is developed by the developing device (13) using the developer of the present invention to form a toner image. Next, the toner image formed on the peripheral surface of the photoconductor (11) is synchronized with the rotation of the photoconductor (11), and the photoconductor (11) and the transfer device (not shown) are fed from the paper feed unit (not shown). ) Are sequentially transferred onto a transfer sheet which is a recording medium fed during (). Further, the transfer paper onto which the toner image has been transferred is separated from the peripheral surface of the photoreceptor (11), introduced into a fixing device (not shown) and fixed, and then copied as a copy (copy) of the image forming apparatus. Printed out. On the other hand, after the toner image is transferred, the surface of the photoconductor (11) is cleaned by the cleaning device (14) to remove the remaining toner, and then the charge is removed by a static eliminator (not shown). Used for image formation.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further more concretely, this invention is not limited to these. “Part” represents part by mass.

(Core manufacturing method)
MnCO ₃ , Mg (OH) ₂ , and Fe ₂ O ₃ powder were weighed and mixed to obtain a mixed powder. This mixed powder was calcined at 900 ° C. for 3 hours in an air atmosphere in a heating furnace, and the obtained calcined product was cooled and pulverized to obtain a powder having a particle diameter of approximately 1 μm. This powder was added with 1% by mass of a dispersant together with water to form a slurry, and this slurry was supplied to a spray dryer and granulated to obtain a granulated product having an average particle size of about 40 μm. This granulated product was loaded into a firing furnace and fired at 1250 ° C. for 5 hours in a nitrogen atmosphere. The obtained fired product was pulverized with a pulverizer, and the particle size was adjusted by sieving to obtain spherical ferrite particles C1 having a volume average particle size of about 35 μm.
The volume average particle size is set to a material refractive index of 2.42, a solvent refractive index of 1.33, and a concentration of about 0.06 in water using a Microtrac particle size distribution model HRA9320-X100 (manufactured by Nikkiso Co., Ltd.). Measured.

(Conductive fine particle production example 1)
1 liter of water was heated to 65 ° C., and a solution of 10.3 g of stannic chloride and 0.08 g of sodium tungstate dissolved in 1.7 liter of 2N hydrochloric acid and 12% by mass aqueous ammonia were added to the suspension. It was added dropwise over 12 minutes so that the pH was 7-8. After dropping, the cake obtained by filtering and washing the suspension was dried at 110 ° C. Next, this dry powder was treated at 500 ° C. for 1 hour in a nitrogen stream.
The obtained fired product is pulverized, and 4% by mass of vinyltriethoxysilane (VTES) is added to the pulverized product with stirring in a Henschel mixer heated to 70 ° C. Further, the treated product was heat-treated at 100 ° C. for 1 hour to obtain conductive fine particles P1 having an average particle diameter of 40 nm and a powder specific resistance of 5.0 Ω · cm.
The average particle size was measured using Nanotrac UPA-EX150 (manufactured by Nikkiso Co., Ltd.) in water at a material refractive index of 1.66 and a solvent refractive index of 1.33.
The powder specific resistance of the conductive fine particles was measured by compressing 5 g of the sample powder at 10 kg / cm ² , connecting an LCR meter AR-480D type manufactured by Keisei Co., Ltd., and measuring the resistance value. In addition, the thickness of the sample at that time was measured and converted into a powder specific resistance value.

(Conductive fine particle production example 2)
In the conductive fine particle production example 1, an average particle diameter of 50 nm and a powder specific resistance of 4.4 g are the same as P1 except that 12.8 g of stannic chloride, 0.10 g of sodium tungstate, and a dropping time of 15 minutes are used. Conductive fine particles P2 of 5 Ω · cm were obtained.

(Conductive fine particle production example 3)
In the conductive fine particle production example 1, the average particle diameter was 100 nm, the powder specific resistance was 4.4, exactly the same as P1, except that 25.7 g of stannic chloride, 0.20 g of sodium tungstate, and the dropping time were 30 minutes. Conductive fine particles P3 of 2 Ω · cm were obtained.

(Conductive fine particle production example 4)
In the conductive fine particle production example 1, except that 77.0 g of stannic chloride, 0.60 g of sodium tungstate, and the dropping time were set to 90 minutes, the average particle size was 300 nm and the powder specific resistance was 4. 9 Ω · cm conductive fine particles P4 were obtained.

(Conductive fine particle production example 5)
In the conductive fine particle production example 1, an average particle size of 330 nm and a powder specific resistance of 5.47 g were obtained in the same manner as P1 except that 84.7 g of stannic chloride, 0.66 g of sodium tungstate, and the dropping time were set to 99 minutes. 4 Ω · cm conductive fine particles P5 were obtained.

(Conductive fine particle production example 6)
In the conductive fine particle production example 3, except that vinyltriethoxysilane was changed to n-octyltriethoxysilane (n-OTES), the same as P3, the average particle diameter was 100 nm, and the powder specific resistance was 12.1 Ω · cm. Conductive fine particles P6 were obtained.

(Conductive fine particle production example 7)
In the conductive fine particle production example 3, in the same manner as P3 except that vinyltriethoxysilane was changed to p-styryltrimethoxysilane (p-STMS), the average particle size was 100 nm and the powder specific resistance was 11.4 Ω · cm. Conductive fine particles P7 were obtained.

(Conductive fine particle production comparative example 1)
In the conductive fine particle production example 3, conductive fine particles P1 ′ having an average particle diameter of 100 nm and a powder specific resistance of 4.3 Ω · cm were obtained in the same manner as P3 except that the surface treatment was not performed.

(Conductive fine particle production example 8)
100 g of aluminum oxide (AKP-30 manufactured by Sumitomo Chemical Co., Ltd.) was dispersed in 1 liter of water to form a suspension, and this liquid was heated to 65 ° C. A suspension of 12.8 g of stannic chloride and 0.10 g of sodium tungstate in 1.7 liters of 2N hydrochloric acid and 12% by mass aqueous ammonia is added to the suspension so that the pH of the suspension is 7-8. Over 15 minutes. After dropping, the cake obtained by filtering and washing the suspension was dried at 110 ° C. Next, this dry powder was treated at 500 ° C. for 1 hour in a nitrogen stream.
The obtained fired product is pulverized, and 4% by mass of vinyltriethoxysilane is added with stirring in a Henschel mixer heated to 70 ° C. Further, the treated product was heat-treated at 100 ° C. for 1 hour to obtain conductive fine particles P8 having an average particle size of 330 nm and a powder specific resistance of 8.1 Ω · cm.

[Carrier Production Example 1]
(Carrier coating layer)
Silicone resin solution [solid content 20% by mass (SR2410: manufactured by Toray Dow Corning Silicone)] 648 parts Titanium catalyst [solid content 60% by mass (TC-750: manufactured by Matsumoto Fine Chemicals)] 4 parts by weight Aminosilane [Solid content 100% by mass (SH6020: manufactured by Toray Dow Corning Silicone)] 3.2 parts, 110 parts of conductive fine particles P1 and 1000 parts of toluene are dispersed with a homomixer for 10 minutes to mix acrylic resin and silicone resin A coating film forming solution was obtained. C1: 5000 parts were used as the core material, and the above coating film forming solution was applied to the surface of the core material at a coater temperature of 55 ° C. with a Spira coater (manufactured by Okada Seiko Co., Ltd.) and dried. . The obtained carrier was fired in an electric furnace at 200 ° C. for 1 hour.
After cooling, the ferrite powder bulk was crushed using a sieve having an aperture of 63 μm to obtain a carrier 1 having a volume average particle size of 36 μm and a volume resistivity of 13.2 (Log Ω · cm).
The volume average particle size is set to a material refractive index of 2.42, a solvent refractive index of 1.33, and a concentration of about 0.06 in water using a Microtrac particle size distribution model HRA9320-X100 (manufactured by Nikkiso Co., Ltd.). Measured.

  The volume resistivity is determined from the fluororesin container (2) containing the electrode (1a) and the electrode (1b) having a surface area of 2.5 cm × 4 cm with a distance of 0.2 cm using the cell shown in FIG. After filling the cell with carrier (3), tapping 10 times at a drop height of 1 cm and a tapping speed of 30 times / minute, a DC voltage of 1000 V was applied between the electrodes (1a) and (1b). The resistance value r [Ω] 30 seconds after application is measured using a high resistance meter 4329A (manufactured by Yokogawa Hewlett-Packard Company), and the volume resistivity [Ω · cm] is calculated from the following equation (2). did.

(Carrier Production Example 2)
In Carrier Production Example 1, Carrier 2 having a volume average particle diameter of 36 μm and a volume resistivity of 13.1 LogΩ · cm was obtained in the same manner as Carrier 1 except that P2 was changed to 110 parts as conductive fine particles.

(Carrier Production Example 3)
In Carrier Production Example 1, Carrier 3 having a volume average particle size of 36 μm and a volume resistivity of 13.1 LogΩ · cm was obtained in the same manner as Carrier 1 except that P3 was changed to 110 parts as conductive fine particles.

(Carrier Production Example 4)
In Carrier Production Example 1, Carrier 4 having a volume average particle size of 36 μm and a volume resistivity of 13.3 LogΩ · cm was obtained in the same manner as Carrier 1 except that P4 was changed to 110 parts as conductive fine particles.

(Carrier Production Example 5)
In Carrier Production Example 1, Carrier 5 having a volume average particle size of 36 μm and a volume resistivity of 13.2 LogΩ · cm was obtained in exactly the same manner as Carrier 1 except that P5 was changed to 110 parts as conductive fine particles.

(Carrier Production Example 6)
In Carrier Production Example 1, Carrier 6 having a volume average particle diameter of 36 μm and a volume resistivity of 13.5 LogΩ · cm was obtained in the same manner as Carrier 1 except that P6 was changed to 110 parts as conductive fine particles.

(Carrier Production Example 7)
In Carrier Production Example 1, Carrier 7 having a volume average particle size of 36 μm and a volume resistivity of 13.5 LogΩ · cm was obtained in the same manner as Carrier 1 except that P7 was changed to 110 parts as conductive fine particles.

(Carrier Manufacturing Comparative Example 1)
In Carrier Production Example 1, Carrier 1 ′ having a volume average particle size of 36 μm and a volume resistivity of 13.1 LogΩ · cm was obtained in exactly the same manner as Carrier 1 except that P1 ′ was changed to 110 parts as conductive fine particles. .

(Carrier Production Example 8)
In Carrier Production Example 1, Carrier 8 having a volume average particle diameter of 36 μm and a volume resistivity of 13.3 LogΩ · cm was obtained in the same manner as Carrier 1 except that P8 was changed to 110 parts as conductive fine particles.
The obtained carrier properties are shown in Table 1.

(Example of toner production)
[Synthesis Example of Polyester Resin A]
443 parts of PO adduct of bisphenol A (hydroxyl value 320), 135 parts of diethylene glycol, 422 parts of terephthalic acid, and 2.5 parts of dibutyltin oxide are placed in a reaction vessel equipped with a thermometer, stirrer, cooler and nitrogen introduction tube. Then, the reaction was carried out at 200 ° C. until the acid value reached 10 to obtain [Polyester resin A]. The resin had a Tg of 63 ° C. and a peak number average molecular weight of 6000.

[Synthesis example of polyester resin B]
443 parts of PO adduct of bisphenol A (hydroxyl value 320), 135 parts of diethylene glycol, 422 parts of terephthalic acid, and 2.5 parts of dibutyltin oxide are placed in a reaction vessel equipped with a thermometer, stirrer, cooler and nitrogen introduction tube. Then, the reaction was carried out at 230 ° C. until the acid value became 7, to obtain [Polyester Resin B]. The resin had a Tg of 65 ° C. and a peak number average molecular weight of 16000.

[Manufacture of base toner particles 1]
· Polyester resin A · · · 40 parts · Polyester resin B · · · 60 parts · Carnauba wax · · · 1 part · Carbon black (# 44 manufactured by Mitsubishi Chemical Corporation) · · · 15 parts The materials are mixed with a Henschel mixer (Mitsui Mining Co., Ltd., Henschel 20B, 1500 rpm for 3 minutes) and kneaded with a single-screw kneader (Buss Co., Ltd. small bus-co-kneader) under the following conditions (set temperature) : Feeder: 2 kg / Hr) at an inlet portion of 100 ° C. and an outlet portion of 50 ° C., and [Base toner A1] was obtained.

Further, the [base toner A1] was kneaded and then cooled by rolling, pulverized by a pulverizer, and further an I-type mill (IDS-2 type manufactured by Nippon Pneumatic Co., Ltd., using a flat impact plate, air pressure: 6.8 atm). / Cm ² , feed amount: 0.5 kg / hr) was finely pulverized, and further classified (132MP manufactured by Alpine) to obtain [base toner particles 1].

(External additive treatment)
To 100 parts of “base toner particle 1”, 1.0 part of hydrophobic silica fine particles (R972: manufactured by Nippon Aerosil Co., Ltd.) was added as an external additive and mixed with a Henschel mixer to obtain toner particles (hereinafter “toner toner”). 1 ”).

[Creation of developers 1-8, 1 ']
7.0 parts of the toner 1 (7.2 μm) obtained in the toner production example is added to the carriers 1 to 8, 1 ′ (93 parts) obtained in the carrier production example, and stirred for 20 minutes by a ball mill. Developers 1-8 and 1 ′ were prepared.

(Developer characteristics evaluation)
Using the developer thus obtained, image evaluation was carried out in an environment of a temperature of 40 ° C. and a humidity of 70% using a Ricoh Pro C901 (Ricoh Digital Color Copier / Printer Combined Machine) manufactured by Ricoh. Specifically, first, using the developers 1 to 8, 1 ′ of Examples and Comparative Examples, printing was performed up to 1 million sheets with an image area ratio of 20%, and various evaluations were performed.

(1) Volume Specific Resistance Change The initial volume specific resistance (LogR1) of the carrier is a common logarithm of the volume specific resistance of the carrier measured in the same manner as in the above [Volume Specific Resistance]. The volume specific resistance (LogR2) of the carrier after running 1,000,000 sheets was measured in the same manner as described above except that the carrier from which the toner of each color in the developer after running was removed using a blow-off device.
The volume specific resistance difference (LogR2−LogR1) after printing 1 million sheets after the initial printing was evaluated according to the following criteria.
0 or more to less than 0.2: ○ (good)
0.2 or more and less than 0.5: △ (can be used)
0.5 or more: × (defect)

(2) Edge carrier adhesion If carrier adhesion occurs, it may cause damage to the photosensitive drum and the fixing roller, resulting in a decrease in image quality. Even if carrier adhesion occurs on the photoconductor, only a part of the carrier is transferred to the paper, and thus evaluation was made by the following method.
After printing 1 million sheets, an image (10 mm) of Ricoh Pro C901 under development conditions (charging potential (Vd): -700 V, potential after exposure of a portion corresponding to an image portion (edge portion): -200 V, development bias: DC-500 V) The number of carriers attached to the edge portion of a solid image of × 10 mm was counted on the photoconductor to evaluate the edge carrier attachment.
The symbols described in the table are ○: good, Δ: usable, ×: bad.

(3) Toner scattering After printing 1 million sheets, the state of toner scattered from the developing portion to the outside of the developing portion was visually evaluated according to the following criteria.
No scattering, or a slight amount of toner is attached to the outside of the development area: ○ (Good)
Toner is attached to the development area, but is not scattered outside the machine: △ (can be used)
Scattered outside the machine: × (defect)

  The results of each evaluation are shown in Table 2.

  From the results of Table 2, the carrier of the present invention of the example is superior to the comparative example in volume resistivity change amount, edge carrier adhesion, and toner scattering, and shows high image quality and high durability even under high temperature and high humidity. I understood.

DESCRIPTION OF SYMBOLS 1a Electrode 1b Electrode 2 Fluororesin container 3 Carrier 10 Process cartridge 11 Photoconductor 12 Charging device 13 Developing device 14 Cleaning device

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 2001-343790 A JP 2007-17838 A JP-A-2015-179258

Claims (8)

A carrier having a core and a coating layer covering the core,
The coating layer includes conductive fine particles,
The carrier, wherein the conductive fine particles include tungsten-doped tin oxide subjected to a surface treatment.   The carrier according to claim 1, wherein a primary particle size of the tungsten-doped tin oxide is 50 nm to 300 nm.   A two-component developer comprising the carrier according to claim 1 or 2 and a toner.   The two-component developer according to claim 3, wherein the toner is a color toner.   A replenishment developer containing a carrier and a toner, wherein the toner is contained in an amount of 2 to 50 parts by weight with respect to 1 part by mass of the carrier, and the carrier is the carrier according to any one of claims 1 to 4. A developer for replenishment characterized by.   An electrostatic latent image carrier, charging means for charging the electrostatic latent image carrier, exposure means for forming an electrostatic latent image on the electrostatic latent image carrier, and on the electrostatic latent image carrier A developing means for developing the electrostatic latent image formed on the toner using the two-component developer according to claim 3 to form a toner image, and a toner image formed on the electrostatic latent image carrier An image forming apparatus comprising: transfer means for transferring the toner image to a recording medium; and fixing means for fixing the toner image transferred to the recording medium.   5. The electrostatic latent image carrier, a charging member for charging the surface of the electrostatic latent image carrier, and an electrostatic latent image formed on the electrostatic latent image carrier, according to claim 3 or 4. A process cartridge comprising: a developing section that develops using a component developer; and a cleaning member that cleans the electrostatic latent image carrier. The step of forming an electrostatic latent image on the electrostatic latent image carrier and the electrostatic latent image formed on the electrostatic latent image carrier using the two-component developer according to claim 3 or 4. A step of developing to form a toner image, a step of transferring the toner image formed on the electrostatic latent image carrier to a recording medium, and a step of fixing the toner image transferred to the recording medium. An image forming method.