JP2009251584A - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device and image forming apparatus, which provides, for a long time, a high quality image free from development history (ghost), by using a hybrid development system with a toner recovering developer carrier, and by then maintaining the capability to recover toner. <P>SOLUTION: A regulating member for charging toner in developer is disposed opposite the toner recovering developer carrier, thereby making it easy for toner to be reattached to carrier. This prevents accumulation of toner on the surface of the toner recovering developer carrier and degradation in the capability to recover toner in a toner recovery area. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention uses a developer containing a carrier and toner, and supplies a toner carrier for supplying toner to the toner carrier, and a toner carrier for developing a latent image with the supplied toner. The present invention relates to a hybrid developing device provided with a toner collecting developer carrying member for collecting undeveloped toner from a toner carrying member, and an image forming apparatus using the same.

  Conventionally, as a developing method in an image forming apparatus using an electrophotographic method, a one-component developing method using only toner as a developer and a two-component developing method using toner and a carrier are known.

  The one-component development system is advantageous in terms of simplification, miniaturization, and cost reduction of the apparatus, but the deterioration of the toner is likely to be accelerated by the strong stress of the regulating part that charges the toner, and the charge acceptability of the toner is reduced. It's easy to do. Further, the toner regulating member and the surface of the toner carrying member are contaminated with the toner and the external additive, so that the charge imparting property to the toner is also lowered, and as a result, the life of the developing device is shortened.

  In the two-component development system, the toner is charged by frictional charging by mixing with the carrier, so that the stress is small and it is advantageous for the deterioration of the toner. Furthermore, since the surface area of the carrier is large, it is relatively strong against contamination by toner and external additives, which is advantageous for extending the life.

  However, in the two-component development method, when developing the electrostatic latent image on the image carrier, the surface of the image carrier is rubbed with the magnetic brush of the developer, so that a magnetic brush mark may be generated. Furthermore, there is a problem that the carrier easily adheres to the image carrier and causes an image defect.

  As a development method that solves the problem of image defects while having the long-life characteristics of the two-component development method, the two-component developer is supported on the developer carrier, and only the toner from the two-component developer is changed to the toner carrier. A so-called hybrid development system that is supplied and used for development is disclosed (see Patent Document 1).

  However, the hybrid development system has a problem that undeveloped toner that has not been used for development on the toner carrier appears on the image as a development history (ghost) in the next development process. This is because priority is given to supplying a toner necessary for development to the toner carrying member by applying a bias to the developer carrying member, and thus the developer carrying member does not have sufficient ability to collect the development residual toner. is doing.

  In recent years, in order to solve this problem, there has been proposed a method in which a developer collecting member for collecting toner is added and a voltage for collecting the development residual toner on the toner carrying member is applied in the hybrid developing method (see Patent Document 2). ). According to the technique described in Patent Document 2, the development residual toner on the toner carrying member can be reliably collected by the toner collecting developer carrying member, so that the problem of development history (ghost) does not occur in the initial stage.

  However, in this method, since the voltage for attracting the toner is always applied in the direction of the toner collecting developer carrier, the toner in the developer is separated from the carrier, and the toner moves to the surface of the toner collecting developer carrier. In addition, uneven distribution of toner occurs.

  When the toner is unevenly distributed on the surface of the toner collecting developer carrier, the unevenly distributed toner remains on the surface of the toner collecting developer carrier when the developer is removed from the toner collecting developer carrier. To do. As a result, the toner is accumulated on the developer carrying member for collecting the toner by repeated use.

Accumulation of charged toner obstructs the recovery electric field in the toner recovery area and lowers the toner recovery capability. For this reason, the recovery capability that was initially sufficient does not last for a long period of time, and ghosting becomes a problem as image formation is repeated.
JP-A-5-150636 JP-A-10-319708

  As described above, technical improvements have been made to cope with ghosting in the hybrid development method, but no technology that sufficiently satisfies the requirements has been proposed.

  Accordingly, an object of the present invention is to solve the above-mentioned problems, use a hybrid developing system provided with a developer collecting member for collecting toner, maintain the toner collecting ability, and generate a high quality with no development history (ghost). It is an object of the present invention to provide a developing device and an image forming apparatus that can obtain an image over a long period of time.

  In order to solve the above problems, the present invention has the following characteristics.

  1. A developer tank containing a developer containing toner and a carrier; a toner supply developer carrier for carrying and conveying the developer mixed and stirred in the developer tank to the surface; and the toner supply developer carrier A toner carrier for receiving and supplying the toner from the body to develop the latent image on the image carrier, and a developer carrier for collecting toner for collecting the development residual toner from the toner carrier. A developing device comprising: a regulating member that is disposed to face the developer carrying member for collecting toner and that regulates the transport amount of the developer.

  2. The toner supply developer carrier and the toner collection developer carrier are respectively disposed on opposite sides of the toner collection developer carrier to the toner supply developer carrier. A magnetic pole for delivering the developer mixed and stirred in the developer tank, and the development after the toner is supplied from the toner supply developer carrier to the toner collection developer carrier. 2. The developing device according to 1, further comprising a magnetic pole for delivering the agent.

  3. The toner collecting developer carrier is provided with a power source for applying a bias voltage in a direction to move the toner toward the toner collecting developer carrier between the toner carrier and the toner carrier. 3. The developing device according to 1 or 2.

  4). A power supply for applying a bias voltage in a direction to move the toner toward the toner carrier between the toner carrier and the developer carrier for collecting toner, and a developer carrier for supplying toner And a power source for applying a bias voltage in a direction to move the toner to the toner carrier side with the toner carrier, and an average value of the bias voltage applied to the toner collecting developer carrier is 3. The developing device according to 1 or 2, wherein an absolute value and an average value of a bias voltage applied to the toner supply developer carrier are the same or small.

  5). An image forming apparatus comprising the developing device according to any one of 1 to 4.

  According to the present invention, the toner collection developer carrier can reliably collect the development residual toner on the toner carrier and can avoid accumulation of toner on the toner collection developer carrier. A stable toner layer is supplied on the body.

  Accordingly, it is possible to provide a developing device and an image forming apparatus that can obtain a high-quality image that maintains the toner recovery capability and does not cause a ghost problem over a long period of time.

  Embodiments of the present invention will be described below with reference to the drawings.

(Configuration and operation of image forming apparatus)
FIG. 1 shows a configuration example of a main part of an image forming apparatus according to an embodiment of the present invention. The schematic configuration and operation of the image forming apparatus will be described with reference to FIG.

  The image forming apparatus is a printer that performs image formation by transferring a toner image formed on an image carrier (photosensitive member) 1 to a transfer medium P such as paper by an electrophotographic method.

  The image forming apparatus includes an image carrier 1 for carrying an image. Around the image carrier 1, a charging member 3 for charging the image carrier 1 and an image carrier 1 are provided. A developing device 2 a for developing an electrostatic latent image, a transfer roller 4 for transferring a toner image on the image carrier 1, and a cleaning blade 5 for removing residual toner on the image carrier 1 are provided on the image carrier 1. They are arranged in order along the rotation direction A.

  The image carrier 1 is charged by the charging member 3 and then exposed by an exposure device 30 equipped with a laser emitter or the like at the point E in the figure, and an electrostatic latent image is formed on the surface thereof. . The developing device 2a develops the electrostatic latent image to form a toner image. The transfer roller 4 transfers the toner image on the image carrier 1 to the transfer medium P, and then discharges it in the direction of arrow C in the figure. The cleaning blade 5 removes the residual toner on the image carrier 1 after the transfer with a mechanical force.

  For the image carrier 1, the charging member 3, the exposure device 30, the transfer roller 4, the cleaning blade 5 and the like used in the image forming apparatus, a well-known electrophotographic technique may be arbitrarily used. For example, although a charging roller is shown as the charging member 3 in the figure, a charging device that is not in contact with the image carrier 1 may be used. Further, for example, there may be no cleaning blade.

  Next, a configuration example of the developing device 2a of the hybrid developing system according to the present embodiment will be described.

  The developing device 2a includes the following components. That is, a developer tank 16 that contains a developer 24 containing toner and a carrier, a toner supply developer carrier 11 that carries and conveys the developer 24 supplied from the developer tank 16 on the surface, and a toner supply development. The toner is supplied from the agent carrier 11 in the toner supply region 7, and develops the electrostatic latent image formed on the image carrier 1. After passing through the development region 6, the toner carrier 25 A toner collecting developer carrier 26 for collecting the undeveloped toner remaining in the toner collecting area 8.

  The developing device 2a also includes a toner carrier bias power source 31 that supplies a voltage to the toner carrier 25, a toner carrier bias power source 32 that supplies a voltage to the toner supply developer carrier 11, and a toner recovery unit. A developer recovery member bias power source 33 for supplying a voltage to the developer carrier 26 and a control device 34 for controlling these power sources.

  The detailed configuration and operation of the developing device 2a will be described later.

(Developer composition)
The configuration of the developer used in the developing device according to this embodiment will be described.

  The developer 24 used in the present embodiment includes toner and a carrier for charging the toner.

<Toner>
The toner is not particularly limited, and a known toner that is generally used can be used, and a colorant, a charge control agent, a release agent, and the like are contained in the binder resin, and external additives are added. What processed the agent can be used. The toner particle diameter is not limited to this, but is preferably about 3 to 15 μm.

  In producing such a toner, it can be produced by a publicly known method. For example, it can be produced using a pulverization method, an emulsion polymerization method, a suspension polymerization method or the like.

  The binder resin used in the toner is not limited to this. For example, styrene resin (monopolymer or copolymer containing styrene or a styrene-substituted product), polyester resin, epoxy resin, vinyl chloride Resins, phenol resins, polyethylene resins, polypropylene resins, polyurethane resins, silicone resins and the like can be mentioned. It is preferable to use those having a softening temperature in the range of 80 to 160 ° C. and those having a glass transition point in the range of 50 to 75 ° C., depending on the resin alone or the composite.

  Further, as the colorant, known ones that are generally used can be used. For example, carbon black, aniline black, activated carbon, magnetite, benzine yellow, permanent yellow, naphthol yellow, phthalocyanine blue, first sky blue, ultra Marine blue, rose bengal, lake red and the like can be used, and it is generally preferable to use them in a proportion of 2 to 20% by mass with respect to the binder resin.

  As the charge control agent, known ones can be used. Examples of the charge control agent for positively chargeable toners include nigrosine dyes, quaternary ammonium salt compounds, triphenylmethane compounds, imidazoles. System compounds and polyamine resins. Examples of the charge control agent for negatively chargeable toners include metal-containing azo dyes such as Cr, Co, Al, and Fe, salicylic acid metal compounds, alkyl salicylic acid metal compounds, and curlyx arene compounds. In general, the charge control agent is preferably used in a proportion of 0.1 to 10% by mass with respect to the binder resin.

  In addition, as the above-mentioned mold release agent, known ones that are generally used can be used. For example, polyethylene, polypropylene, carnauba wax, sazol wax and the like can be used alone or in combination of two or more. In general, it is preferably used at a ratio of 0.1 to 10% by mass with respect to the binder resin.

  Also, as the above external additives, publicly known ones can be used, and fluidity improvement, for example, inorganic fine particles such as silica, titanium oxide, aluminum oxide, acrylic resin, styrene resin, silicone resin In addition, resin fine particles such as a fluororesin can be used, and it is particularly preferable to use one that has been hydrophobized with a silane coupling agent, a titanium coupling agent, silicone oil or the like. Such a fluidizing agent is added to the toner at a ratio of 0.1 to 5% by mass and used. The number average primary particle size of the external additive is preferably 10 to 100 nm.

  Further, as the external additive, reverse polarity particles having a chargeability opposite to that of the toner may be used. The reverse polarity particles preferably used are appropriately selected depending on the charging polarity of the toner.

  When a negatively chargeable toner is used as the toner, fine particles having positive chargeability are used as the opposite polarity particles. For example, inorganic fine particles such as strontium titanate, barium titanate, and alumina, acrylic resin, benzoguanamine resin, nylon ( Fine particles made of thermoplastic resin such as (registered trademark) resin, polyimide resin, polyamide resin or thermosetting resin can be used. Further, a positive charge control agent imparting positive chargeability may be contained in the resin, or a copolymer of nitrogen-containing monomers may be constituted.

  As the positive charge control agent, for example, nigrosine dye, quaternary ammonium salt and the like can be used, and as the nitrogen-containing monomer, 2-dimethylaminoethyl acrylate, 2-diethylaminoethyl acrylate, 2-Dimethylaminoethyl methacrylate, 2-diethylaminoethyl methacrylate, vinylpyridine, N-vinylcarbazole, vinylimidazole and the like can be used.

  On the other hand, in the case of using a positively chargeable toner, fine particles having negative chargeability are used as the reverse polarity particles. For example, in addition to inorganic fine particles such as silica and titanium oxide, fluorine resin, polyolefin resin, silicone resin, polyester resin Fine particles composed of a thermoplastic resin such as a thermosetting resin or the like can be used. Further, a negative charge control agent imparting negative chargeability may be contained in the resin, or a copolymer of a fluorine-containing acrylic monomer or a fluorine-containing methacrylic monomer may be constituted. Examples of the negative charge control agent include salicylic acid-based and naphthol-based chromium complexes, aluminum complexes, iron complexes, and zinc complexes.

  In addition, in order to control the chargeability and hydrophobicity of the reverse polarity particles, the surface of the inorganic fine particles may be surface treated with a silane coupling agent, a titanium coupling agent, silicone oil, etc. When imparting positive chargeability, surface treatment with an amino group-containing coupling agent is preferred, and when imparting negative chargeability, surface treatment with a fluorine group-containing coupling agent is preferred.

  The number average particle diameter of the reverse polarity particles is preferably 100 to 1000 nm. It is used by adding 0.1 to 10% by mass with respect to the toner.

<Carrier>
The carrier is not particularly limited, and a commonly used carrier can be used, and a binder type carrier, a coat type carrier, and the like can be used. The carrier particle size is not limited to this, but is preferably 15 to 100 μm.

  The binder type carrier is obtained by dispersing magnetic fine particles in a binder resin, and positive or negative chargeable fine particles can be fixed to the carrier surface or a surface coating layer can be provided. The charging characteristics such as the polarity of the binder type carrier can be controlled by the material of the binder resin, the chargeable fine particles, and the type of the surface coating layer.

  Examples of the binder resin used in the binder-type carrier include thermoplastic resins such as vinyl resins, polyester resins, nylon resins, polyolefin resins, and the like typified by polystyrene resins, and curable resins such as phenol resins. .

  Magnetic fine particles of the binder type carrier include spinel ferrite such as magnetite and gamma iron oxide, and magnets such as spinel ferrite and barium ferrite containing one or more metals other than iron (Mn, Ni, Mg, Cu, etc.). Plumbite type ferrite, iron or alloy particles having an oxide layer on the surface can be used. The shape may be granular, spherical, or needle-shaped. In particular, when high magnetization is required, it is preferable to use iron-based ferromagnetic fine particles. In consideration of chemical stability, it is preferable to use ferromagnetic fine particles of magnetoplumbite type ferrite such as spinel ferrite and barium ferrite containing magnetite and gamma iron oxide. A magnetic resin carrier having a desired magnetization can be obtained by appropriately selecting the type and content of the ferromagnetic fine particles. The magnetic fine particles are suitably added to the magnetic resin carrier in an amount of 50 to 90% by mass.

  Silicone resin, acrylic resin, epoxy resin, fluorine resin, etc. are used as the surface coating material of the binder type carrier, and these resins are coated on the surface and cured to form a coating layer, thereby providing a charge imparting ability. Can be improved.

  For example, the charging fine particles or the conductive fine particles are fixed to the surface of the binder type carrier by, for example, mixing the magnetic resin carrier and the fine particles uniformly, adhering these fine particles to the surface of the magnetic resin carrier, and then mechanically and thermally. By applying a strong impact force and fixing the fine particles so as to be driven into the magnetic resin carrier. In this case, the fine particles are not completely embedded in the magnetic resin carrier, but are fixed so that a part thereof protrudes from the surface of the magnetic resin carrier.

  As the chargeable fine particles, organic or inorganic insulating materials are used. Specifically, organic insulating fine particles such as polystyrene, styrene copolymer, acrylic resin, various acrylic copolymers, nylon, polyethylene, polypropylene, fluororesin, and cross-linked products thereof may be used as the organic type. Regarding the charge level and polarity, a desired level of charge and polarity can be obtained by a material, a polymerization catalyst, surface treatment, and the like. Further, as the inorganic type, negatively charged inorganic fine particles such as silica and titanium dioxide, and positively charged inorganic fine particles such as strontium titanate and alumina are used.

  On the other hand, a coated carrier is a carrier in which a carrier core particle made of a magnetic material is coated with a resin, and in a coated carrier, like a binder carrier, positive or negatively chargeable fine particles are fixed on the carrier surface. it can. Charging characteristics such as polarity of the coat type carrier can be controlled by the type of the surface coating layer and the chargeable fine particles, and the same material as the binder type carrier can be used. In particular, the coating resin can be the same resin as the binder resin of the binder type carrier.

  The mixing ratio of the toner and the carrier may be adjusted so as to obtain a desired toner charge amount. The mixing ratio of the toner is 3 to 50% by mass, preferably 6 to 30% by mass with respect to the total amount of the toner and the carrier. Is suitable.

(Configuration and operation of developing device 2a)
A detailed configuration example and operation example of the developing device 2a according to the present embodiment will be described with reference to FIG.

<Device configuration>
The developer 24 used in the developing device 2a is composed of toner and carrier as described above, and is stored in the developer tank 16.

  The developer tank 16 is formed by a casing 19 and normally contains mixing and agitating members 17 and 18 therein. The mixing stirring members 17 and 18 mix and stir the developer 24 and supply the developer 24 to the toner supply developer carrier 11. An ATDC (Automatic Toner Density Control) sensor 20 for detecting the toner concentration is preferably disposed at a position of the casing 19 facing the mixing and agitating member 18.

  The developing device 2 a normally has a replenishing unit 10 for replenishing the developer tank 16 with the toner consumed in the developing area 6. In the replenishing unit 10, the replenishing toner 23 sent from a hopper (not shown) containing the replenishing toner 23 is replenished into the developer tank 16.

  The developing device 2a is also provided with a regulating member for thinning the developer, which is disposed to face the developer collecting body 26 for collecting the toner and regulates the amount of the developer conveyed on each developer carrying body. (Regulating blade) 15 is provided. In the developing device 2a of this embodiment, the developer is temporarily held by the toner collecting developer carrier 26 and delivered to the toner supply developer carrier 11. Thereby, the regulating member 15 is arranged to face the toner collecting developer carrier 26.

  The toner supply developer carrier 11 includes a magnet body 13 that is fixedly arranged and a rotatable sleeve roller 12 that encloses the magnet body 13, and supplies toner to the toner carrier 25 during image formation. A toner supply bias is applied by a toner supply developer carrier bias power supply 32.

  The magnet body 13 has six magnetic poles N1, S1, N2, S2, N3, and S3 along the rotation direction of the sleeve roller 12. Of these magnetic poles, the main magnetic pole N <b> 1 is disposed at the position of the toner supply region 7 facing the toner carrier 25.

  Similarly, the toner collecting developer carrier 26 is composed of a magnet body 28 that is fixedly arranged and a rotatable sleeve roller 27 that encloses the magnet body 28, and for collecting the development residual toner on the toner carrier 25. A toner collection bias is applied by a toner collection developer carrier bias power supply 33.

  The magnet body 28 has five magnetic poles S4, N5, S5, S6, and N4 along the rotation direction of the sleeve roller 27. Of these magnetic poles, the main magnetic pole S <b> 4 is disposed at the position of the toner recovery region 8 facing the toner carrier 25.

  Further, in the developing device 2a, in order to transfer the developer 24 on the toner collection developer carrier 26 to the toner supply developer carrier 11, each of the S6 pole and the N2 pole serves as a toner collection developer. The carrier 26 and the developer carrier 11 for supplying toner are arranged at opposing portions. The developer 24 is delivered and transported from the S6 magnetic pole side of the toner collecting developer carrier 26 to the N2 magnetic pole side of the toner supply developer carrier 11.

  Further, in order to deliver the developer 24 on the toner supply developer carrier 11 after having been once delivered and supplied to the toner carrier 25 to the toner collection developer carrier 26, respectively. The S1 pole and the N4 pole of the toner supply developer carrier 11 and the toner collection developer carrier 26 are arranged opposite to each other. The developer 24 is delivered and transported from the S1 magnetic pole side of the toner supply developer carrier 11 to the N4 magnetic pole side of the toner collection developer carrier 26.

  The toner carrier 25 is disposed so as to face the toner supply developer carrier 11, the toner collection developer carrier 26, and the image carrier 1, and develops the electrostatic latent image on the image carrier 1. A developing bias is applied by a toner carrier bias power source 31.

  The toner carrier 25 may be made of any material as long as the voltage can be applied, and examples thereof include an aluminum roller that has been subjected to a surface treatment such as alumite. In addition, on a conductive substrate such as aluminum, for example, polyester resin, polycarbonate resin, acrylic resin, polyethylene resin, polypropylene resin, urethane resin, polyamide resin, polyimide resin, porsulfone resin, polyether ketone resin, vinyl chloride resin, vinyl acetate You may use what gave resin coatings, such as resin, a silicone resin, a fluororesin, and rubber coatings, such as silicone rubber, urethane rubber, nitrile rubber, natural rubber, and isoprene rubber. The coating material is not limited to this.

  Further, a conductive agent may be added to the bulk or surface of the coating. Examples of the conductive agent include an electronic conductive agent or an ionic conductive agent. Examples of the electronic conductive agent include carbon black such as kettin black, acetylene black, and furnace black, metal powder, and metal oxide fine particles, but are not limited thereto. Examples of the ionic conductive agent include cationic compounds such as quaternary ammonium salts, amphoteric compounds, and other ionic polymer materials. Furthermore, a conductive roller made of a metal material such as aluminum may be used.

<Operation of the device>
An example of the operation of the developing device 2a will be described in detail with reference to FIG.

  The developer 24 in the developer tank 16 is mixed and stirred by the rotation of the mixing and stirring members 17 and 18 and frictionally charged. At the same time, the developer 24 is circulated and transported in the developer tank 16 to the sleeve roller 27 on the surface of the developer carrier 26. Supplied.

  The developer 24 is held on the surface side of the sleeve roller 27 by the magnetic force of the magnet body 28 inside the toner collection developer carrier 26, and rotates together with the sleeve roller 27 to be transferred to the toner collection developer carrier 26. The amount of passage is regulated by the regulating member 15 provided to face. As will be described later, the regulating member 15 also functions to charge the toner on the toner collecting developer carrier 26 and mechanically reattach it to the carrier by rubbing the developer 24 mechanically.

  The developer 24 on the toner collecting developer carrier 26 whose passage amount is regulated by the regulating member 15 is transported to a portion facing the toner supply developer carrier 11. Therefore, the toner is supplied to the toner supply developer carrier 11 by a magnetic field formed by the magnetic pole S6 of the toner collection developer carrier 26 and the magnetic pole N2 of the toner supply developer carrier 11.

  The developer 24 delivered to the toner supply developer carrier 11 rotates and moves together with the sleeve roller 12 of the toner supply developer carrier 11 and is conveyed to the toner supply region 7 facing the toner carrier 25. The

  In the toner supply region 7, developer spikes are formed by the magnetic force of the main magnetic pole N <b> 1 of the magnet body 13, and due to the development bias applied to the toner carrier 25 and the toner supply bias applied to the toner supply developer carrier 11. The toner in the developer 24 is supplied to the toner carrier 25 side by the force applied to the toner by the formed supply electric field.

  The toner layer supplied to the toner carrier 25 is transported to the development region 6 as the toner carrier 25 rotates, and is latentized by the development electric field formed by the development bias and the latent image potential on the image carrier 1. The image is developed into a visible image. The development method may be a reversal development method or a regular development method.

  The toner layer (development residual toner) that has consumed toner in the development area 6 is further conveyed to the toner collection area 8 facing the toner collection developer carrier 26.

  On the other hand, the remaining developer 24 that has supplied the toner to the toner carrier 25 in the toner supply region 7 is conveyed to a portion facing the developer carrier 26 for collecting the toner, and the magnetic pole of the developer carrier 11 for toner supply is conveyed. The toner is transferred to the toner collecting developer carrier 26 by the magnetic field formed by S1 and the magnetic pole N4 of the toner collecting developer carrier 26.

  The developer 24 delivered to the toner collecting developer carrier 26 rotates and moves together with the sleeve roller 27 of the toner collecting developer carrier 26 and is conveyed to the toner collecting region 8 facing the toner carrier 25. The

  In the toner recovery area 8, the force applied to the toner by the recovery electric field formed by the developing bias applied to the toner carrier 25 and the toner recovery bias applied to the toner recovery developer carrier 26, and the ears of the developer 24. Due to the mechanical rubbing force caused by standing, the development residual toner moves from the toner carrier 25 to the developer carrier for toner collection and is collected.

  The developer 24 containing the toner recovered on the toner recovery developer carrier 26 is conveyed toward the developer tank 16 along with the rotation of the sleeve 27, and after passing through the S5 pole of the magnet body 28, the toner recovery development. It is peeled off from the agent carrier 26 and collected into the developer tank 16.

  When a supply control unit (not shown) detects from the output value of the ATDC sensor 20 that the toner concentration in the developer 24 has become equal to or lower than the minimum toner concentration for securing the image density, the toner supply means (not shown) puts the toner in the hopper. The stored supply toner 23 is supplied into the developer tank 16 through the toner supply unit 10.

  Next, a method for controlling the supply and recovery of the toner with the toner carrier by applying a bias voltage to each developer carrier of the developing device 2a will be described. The following bias voltage application is performed by the control device 34 controlling the toner carrier bias power source 31, the toner supply developer carrier bias power source 32, and the toner collection developer carrier bias power source 33. (See FIG. 1).

  At the time of image formation, the toner carrier 25 and the toner supply are formed in the toner supply region 7 so that a supply electric field in which the toner receives a force from the toner carrier 11 to the toner carrier 25 is formed. A bias voltage is applied to the developer carrying member 11.

  For example, if the toner polarity is negative, a voltage lower than that of the toner carrier 25 may be applied to the toner supply developer carrier 11.

  Further, in the toner collection area 8, the toner carrier 25 and the toner collection developer carrier are formed so that a collection electric field is formed in such a direction that the toner receives a force from the toner carrier 25 to the toner collection developer carrier 26. A bias voltage is applied to 26.

  Similarly, if the toner polarity is negative, a higher voltage than the toner carrier 25 may be applied to the toner collection developer carrier 26.

  On the other hand, in the toner collection area 8, a bias voltage is formed so that an electric field in which the toner receives a force from the toner collecting developer carrier 26 to the toner carrier 25, that is, an electric field in the direction of supplying the toner is formed. Can also be applied.

  This has the effect of suppressing toner accumulation on the surface of the developer carrying member 26 for collecting toner, which will be described later. However, in order to maintain the toner recovery capability, at least the average bias voltage applied to the toner supply developer carrier 11 having the same polarity as the bias voltage applied to the toner recovery developer carrier 26 is the average. The absolute value must be the same or smaller than the value.

  The bias voltage applied to the toner carrier 25, the toner supply developer carrier 11, and the toner collection developer carrier 26 may be superimposed on an AC bias in addition to a DC component for any one or a plurality of bias voltages. it can.

  As the AC waveform used at this time, various AC waveforms such as a sine wave, a rectangular wave, and a triangular wave can be used. When an AC bias voltage is used, the bias voltage may be set so that the average value satisfies the above magnitude relationship.

(Regarding prevention of toner accumulation by developer and flow of developer)
Details of the relationship between the toner accumulation due to the uneven distribution of toner in the toner collection area and the function, arrangement, and developer flow of the regulating member for preventing the toner accumulation will be described.

<Regarding toner accumulation>
In the toner collection area 8, conventionally, a developing bias is applied to the toner carrier 25, and a toner collecting bias is applied to the toner collecting developer carrier 26 to form a collecting electric field. By this recovery electric field, the development residual toner moves from the toner carrier 25 to the developer carrier for toner recovery and is recovered.

  However, if this recovery electric field is strong, the toner (protruding) in the developer is separated from the carrier in the toner recovery area 8, and the toner moves to the surface of the toner recovery developer carrier 26, and the toner is unevenly distributed on the surface. Will arise.

  In this state where the toner is unevenly distributed on the surface, when the developer 24 is once removed from the toner collecting developer carrier 26, the unevenly distributed toner remains on the surface of the toner collecting developer carrier. As a result, accumulation of toner occurs on the toner collecting developer carrier 26 by repeated use.

  Accumulation of the charged toner generates a toner layer potential, thereby obstructing the recovery electric field in the toner recovery area 8 and reducing the toner recovery capability. For this reason, the ability to collect the development residual toner does not last for a long time, and ghosting becomes a problem with repeated image formation.

<Regulator function>
In the present embodiment, the regulating member 15 is opposed to the toner collecting developer carrier 26 in order to prevent the uneven distribution of toner on the surface of the toner collecting developer carrier 26 due to the collecting electric field in the toner collecting region 8. Arranged. At the same time, the developer flow is once held by the toner collecting developer carrier 26, the transport amount is regulated by the regulating member 15, and then transferred to the toner supply developer carrier 11. did.

  The arrangement of the regulating member is due to the following reason.

  If the toner collected on the toner collecting developer carrier 26 is attached to the carrier, it returns to the developer tank 16 together with the carrier as a developer and accumulates on the surface of the toner collecting developer carrier 26. Absent. The fact that the collected toner remains unevenly distributed on the surface of the toner collecting developer carrier 26 means that the toner does not reattach to the carrier. This is presumably because, on the surface of the toner collecting developer carrier 26, frictional charging due to friction between the toner and the carrier does not occur, and electrostatic adsorption hardly occurs.

  Therefore, it is considered that reattachment of the toner to the carrier can be promoted by giving a relative speed difference between the carrier and the toner so as to be mechanically rubbed. That is, since the reattached toner returns to the developer tank 16 together with the carrier, accumulation on the surface of the toner collecting developer carrier 26 can also be suppressed.

  The regulating member 15 is used to cause such a rubbing state on the surface of the toner collecting developer carrier 26. Although the regulating member 15 is originally provided to regulate the developer conveyance amount, it can also be used.

  In the developing device 2a according to the present embodiment, the developer flow is temporarily held by the toner collecting developer carrier 26, regulated by the regulating member 15, and then received by the toner supply developer carrier 11. I am trying to pass it. In this way, a regulation member 15 that is conventionally provided to face the toner supply developer carrier 11 in order to regulate the developer conveyance amount is provided to face the toner collection developer carrier 26. It is also used as a member for giving a relative speed difference between the carrier and the toner and triboelectrically charging.

  With such an arrangement, it is possible to reduce the load on the developer by providing the restricting member only at one location and installing it at two or more locations, and to suppress a decrease in the durability of the developer.

  In other words, the use of the regulating member in this way promotes the reattachment of toner to the carrier, thereby preventing toner accumulation on the surface of the developer carrying member for collecting toner and reducing the toner collecting ability in the toner collecting area. Suppress.

  Therefore, the toner collection developer carrier can reliably collect the development residual toner on the toner carrier, and toner accumulation on the toner collection developer carrier can be avoided, so that it is always stable on the toner carrier. The toner layer is supplied. Accordingly, it is possible to provide a developing device and an image forming apparatus that can obtain a high-quality image that maintains the toner recovery capability and does not cause a ghost problem over a long period of time.

<Developer flow>
In the configuration and operation example of the developing device 2a, the developer flow is as follows.

  That is, the toner supply developer carrier 11 and the toner collection developer carrier 26 are arranged to face each other. The developer 24 once supplied from the developer tank 16 onto the toner collection developer carrier 26 is regulated on the toner collection developer carrier 26, and the toner supply developer from the toner collection developer carrier 26 is regulated. Delivered to the carrier 11. After supplying the toner to the toner carrier 25, the toner is again delivered from the toner carrier 11 to the toner collection developer carrier 26, separated from the toner collection developer carrier 26, and returned to the developer tank 16.

  However, the flow of the developer 24 is not limited to the above flow.

  For example, FIG. 2 shows a configuration example of the developing device 2b of the reference example for comparison. In FIG. 2, members having the same functions as those in FIG. 1 are denoted by the same reference numerals as those in FIG.

  In the configuration as shown in FIG. 2, the developer 24 is supplied directly from the developer tank 16 onto the toner supply developer carrier 11 and is regulated on the toner supply developer carrier 11 as it is. After supplying the toner to the toner carrier 25, the toner is transferred from the developer carrier 11 for supplying toner to the developer carrier 26 for collecting toner, separated from the developer carrier 26 for collecting toner, and returned to the developer tank 16.

  In this case, the regulating member 15 ′ is provided opposite to the toner supply developer carrier 11 as shown in the figure.

  Therefore, a configuration for realizing the flow of the developer may be adopted, but a new regulating member 15 may be disposed opposite to the toner collecting developer carrier 26 to form another embodiment according to the present invention. In that case, the regulating member is provided in two places.

  Further, for example, if the regulating members are provided at two locations, the developer 24 is supplied to each of the toner supply developer carrier 11 and the toner collection developer carrier 26 and the amount of conveyance is regulated by each of the toners. The developer 24 is transported to the supply area 7 and the toner collection area 8, and the developer 24 is separated from each developer carrier and returned to the developer tank 16 (toner supply developer carrier 11 and toner collection developer carrier). The flow of the developer with the body 26 may be separated).

  That is, any configuration can be adopted as long as the developer flows on the downstream side of the toner collection region 8 so that the regulating member can be provided to face the developer carrier 26 for collecting the toner.

  The result of image formation performed to confirm the effect using the developing device according to the above-described embodiment will be described.

<Setting conditions>
As the developing devices used, developing devices having configurations corresponding to the developing device 2a according to the embodiment of the present invention shown in FIG. 1 and the conventional developing device 2b shown in FIG. 2 were prepared.

  As the image forming apparatus, a bizhub C350, which is an MFP manufactured by Konica Minolta Business Technologies, Inc., was modified and used with the developing devices 2a and 2b having the configuration shown in FIG. The developer will be described later, but negatively charged toner was used.

  In each developing device, the development gap between the image carrier and the toner carrier was 0.15 mm. The toner supply gap between the toner carrier and the toner supply developer carrier, and the toner collection gap between the toner carrier and the toner collection developer carrier were each 0.3 mm.

  The developing bias voltage applied to the toner carrier was a rectangular wave voltage with an amplitude of peak to peak of 1.4 kV, a DC component of −300 V, a frequency of 4 kHz, and a duty ratio of 50%.

  The supply bias voltage applied to the toner supply developer carrier was DC-500 V, and the recovery bias voltage applied to the toner recovery developer carrier was the voltage specified in the following Examples and Comparative Examples.

  The background potential of the electrostatic latent image formed on the image bearing member was −550V, and the image portion potential was −60V.

Example 1
Using the developing device 2a shown in FIG. 1, a -200V DC voltage was applied to the toner collecting developer carrier, and a potential difference of +100 V was given to the toner carrier.

(Example 2)
Using the developing device 2a shown in FIG. 1, a DC voltage of −400 V was applied to the developer carrier for collecting toner, and a potential difference of −100 V was applied to the toner carrier.

(Example 3)
Using the developing device 2a shown in FIG. 1, an AC voltage having a frequency of 4 kHz and a peak-to-peak amplitude of −600 V is reversed on the toner collecting developer carrier, and the phase of the AC voltage of the toner carrier is inverted by 180 degrees. It was applied in a superimposed manner on a DC voltage of 200V.

  At this time, the peak-to-peak amplitude of the AC component of the voltage applied as a bias in the toner recovery area is 2000V.

(Comparative Example 1)
Using the developing device 2b shown in FIG. 2, a DC voltage of −200 V was applied to the toner collecting developer carrier, and a potential difference of +100 V was given to the toner carrier.

(Comparative Example 2)
Using the developing device 2b shown in FIG. 2, a DC voltage of −400 V was applied to the toner collecting developer carrier, and a potential difference of −100 V was applied to the toner carrier.

<Developer>
As the toner and developer, those prepared as follows were used.

  As a fluidizing agent, 0.2% by mass of the first hydrophobic silica and 0.5% by mass of the second hydrophobic silica are used as a fluidizing agent for the toner base material having a particle size of about 6.5 μm prepared by the wet granulation method. Hydrophobic titanium oxide (0.5% by mass) was subjected to a surface treatment for 3 minutes at a speed of 40 m / s using a Henschel mixer (manufactured by Mitsui Kinzoku Mining Co., Ltd.) as the first external addition treatment.

  The first hydrophobic silica used here is obtained by subjecting silica having an average primary particle size of 16 nm to surface treatment with hexamethyldisilazane (HMDS) as a hydrophobizing agent. The second hydrophobic silica is obtained by surface-treating silica having an average primary particle size of 20 nm with HMDS. Hydrophobic titanium oxide is an anatase-type titanium oxide having an average primary particle size of 30 nm and surface-treated with isobutyltrimethoxysilane as a hydrophobizing agent in an aqueous wet process.

  Subsequently, as the second treatment, 0.5% by mass of the third hydrophobic silica and 2.0% by mass of titanium oxide were treated at 40 m / s for 3 minutes using the same Henschel mixer. The third hydrophobic silica is obtained by surface-treating silica having an average primary particle size of 200 nm with HMDS. The average primary particle diameter of 500 nm was used for aluminum oxide.

  As the developer, the carrier for bizhub C350 (particle size: about 33 μm) and the toner were used. The toner concentration in the developer was 8%. The toner concentration is a ratio of the total mass of the toner and the post-treatment agent to the total mass of the developer.

<Evaluation method>
In each example and comparative example to be described later, the above-described image forming apparatus is used to continuously print 1000 sheets of the chart shown in FIG. 3, and the development history (ghost) of the first and 1000th sheets is determined. Compared.

  In the chart of FIG. 3, 51 is a white portion, 52 is a solid black portion, and 53 is a half image portion. In the white portion 51 and the black solid portion 52, the development residual toner amount generated in a corresponding region of the toner carrier is greatly different. Therefore, if the undeveloped toner is not collected and remains, the influence appears particularly in the half image portion (ghosting) during development after one cycle of the toner carrier.

  3 is an example in which a ghost that does not exist in the chart occurs. A region thinner than the half image portion (having a small amount of toner) is generated at a position after one cycle of the black solid portion.

  The development history (ghost) is evaluated by measuring the density of the black solid portion and the white portion of the printed half image portion (55a and 55b) with a densitometer (X-Rite 310 manufactured by X-Rite). The case where the difference in density was 0.1 or less was evaluated as ◯ (good), and the other case was evaluated as x (occurrence).

  In addition, the developer after the 1000th sheet is taken out to check whether the toner is unevenly distributed on the surface of the developer carrying member for collecting the toner. The surface potential of the toner adhering to the surface was measured.

  When measuring the surface potential, the surface potential meter Model 344 manufactured by TREK was used, and the measurement was performed with the developer carrying member for collecting toner grounded.

(Evaluation results)
The evaluation results of Examples 1 to 3 and Comparative Examples 1 and 2 are shown in Table 1.

  In the table, “developing device” represents either the developing device 2a according to the present embodiment shown in FIG. 1 or the conventional developing device 2b shown in FIG.

  “Recovery ΔVave” represents a value obtained by subtracting the average value (−300 V) of the voltage applied to the toner carrying member from the average value of the voltage applied to the toner collecting developer carrying member (setting differs individually). .

  “The first ghost” is an evaluation based on the above-mentioned criteria for determining the first ghost occurrence status, and “1000th ghost” is an evaluation based on the above-mentioned criteria for determining the ghost occurrence status for the 1000th.

  “Surface potential” is the result of measuring the surface potential between the S5 and S6 poles on the surface of the developer carrying member for toner collection after the 100th sheet.

  In Table 1, the evaluation results of Example 1 and Comparative Example 1 are compared.

  In Example 1, no ghost is generated from the first sheet to the 1000th sheet, and the toner is hardly unevenly distributed on the surface of the toner collecting developer carrying member even after the 1000th sheet is completed.

  On the other hand, in Comparative Example 1, no ghost is generated on the first sheet, but the recovery capability is insufficient due to continuous printing, and a ghost is generated on the 1000th sheet. Further, after the completion of 1000 sheets, the surface potential of the toner collecting developer carrying member becomes high, and it can be seen that uneven distribution of toner occurs.

  In both cases, a bias voltage in the direction of moving the toner toward the toner collecting developer carrying member is applied to the toner collecting developer carrying member (recovery ΔVave is positive). However, a difference in the occurrence of ghost appears depending on the difference in the developing device, that is, whether or not the regulating member is disposed to face the developer carrying member for collecting toner.

  Next, the evaluation results of Example 2 and Comparative Example 2 are compared.

  Also in Example 2, no ghost is generated from the first sheet to the 1000th sheet, and the toner is hardly unevenly distributed on the surface of the developer carrying member for collecting the toner even after the completion of the 1000th sheet.

  On the other hand, in Comparative Example 2, the ghost is not generated in the first sheet, but the recovery capability is insufficient due to continuous printing, and the ghost is generated in the 1000th sheet. Further, after the completion of 1000 sheets, the surface potential of the toner collecting developer carrying member becomes high, and it can be seen that uneven distribution of toner occurs.

  In this case, in both cases, a bias voltage is applied to the developer carrier for collecting the toner in a direction in which the toner is moved to the toner carrier (recovery ΔVave is negative). However, regardless of the direction of the recovery electric field, a difference in the occurrence of ghost appears depending on the difference in the developing device, that is, whether or not the regulating member is disposed to face the developer carrier for toner recovery.

  Thus, even if the electric field is in the reverse direction, the toner collecting ability to the toner collecting developer carrying member can be maintained because the average value of the collection bias voltage applied to the toner collecting developer carrying member is This is because it is the same polarity as the average value of the supply bias voltage applied to the toner supply developer carrier and is smaller.

  The same can be said for Example 3 below.

  In Example 3 as well, no ghost is generated from the first sheet to the 1000th sheet, and the toner is hardly unevenly distributed on the surface of the developer carrying member for collecting the toner even after the 1000th sheet is completed.

  In this case, an AC bias voltage is applied to the toner collecting developer carrying member, and the average value of the voltages is a voltage in a direction in which the toner is moved to the toner collecting developer carrying member.

  As described above, according to the developing device and the image forming apparatus according to the present embodiment, the regulating member for charging the toner in the developer is disposed opposite the toner collecting developer carrier, By promoting re-adhesion to the carrier, toner accumulation on the surface of the developer carrying member for collecting toner is prevented, and a decrease in toner collecting ability in the toner collecting area is suppressed.

  Therefore, the toner collection developer carrier can reliably collect the development residual toner on the toner carrier, and toner accumulation on the toner collection developer carrier can be avoided, so that it is always stable on the toner carrier. The toner layer is supplied. As a result, it is possible to obtain a high-quality image over a long period of time, in which the toner recovery capability is maintained and the ghost problem does not occur.

  In addition, the above-mentioned embodiment is an illustration and restrictive at no points. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 is a cross-sectional view illustrating a configuration example of a main part of a developing device 2a and an image forming apparatus including the same according to an embodiment of the present invention. It is sectional drawing which shows the structural example of the principal part of the image development apparatus provided with the developing device 2b of a reference example, and it. It is a figure which shows the chart for development history evaluation. In addition, an example of a ghost occurrence state during printing is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image carrier 2a, 2b Developing device 3 Charging member 4 Transfer roller 5 Cleaning blade 6 Development area 7 Toner supply area 8 Toner collection area 11 Toner supply developer carrier 12 Sleeve roller 13 Magnet body 15 Restriction member 16 Developer tank 24 Developer 25 Toner Carrier 26 Toner Recovery Developer Carrier 27 Sleeve Roller 28 Magnet Body

Claims (5)

A developer tank containing a developer including toner and a carrier;
A developer carrying member for supplying toner that carries the developer mixed and stirred in the developer tank to the surface; and
A toner carrier that receives and supplies the toner from the toner supply developer carrier and develops a latent image on the image carrier;
A toner collecting developer carrying member for collecting undeveloped toner from the toner carrying member,
A developing device, comprising: a regulating member that is disposed to face the toner collecting developer carrying member and regulates the transport amount of the developer. The toner supply developer carrier and the toner recovery developer carrier are:
Arranged in the opposite part,
A magnetic pole for delivering the developer mixed and stirred in the developer tank from the toner collecting developer carrying member to the toner supplying developer carrying member;
2. A magnetic pole for delivering the developer after the toner is supplied to the toner carrier from the toner supply developer carrier to the toner collecting developer carrier. The developing device according to 1. The toner collecting developer carrier is provided with a power source for applying a bias voltage in a direction to move the toner toward the toner collecting developer carrier between the toner carrier and the toner carrier. The developing device according to claim 1 or 2. A power source for applying a bias voltage in a direction to move the toner toward the toner carrier between the toner carrier and the developer carrier for toner collection;
A power supply for applying a bias voltage in a direction to move the toner toward the toner carrier between the toner carrier and the developer carrier for toner supply;
The average value of the bias voltage applied to the toner collecting developer carrying member is the same as or smaller than the average value of the bias voltage applied to the toner supplying developer carrying member. Item 3. The developing device according to Item 1 or 2. An image forming apparatus comprising the developing device according to claim 1.

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