JP4706442B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device used in an image forming apparatus such as a copying machine or a printer, and an image forming apparatus using the developing device.

  Conventionally, in an image forming apparatus using an electrophotographic method, as a developing method of an electrostatic latent image formed on an image carrier, a one-component developing method using only toner as a developer and a two-component using a toner and a carrier Development methods are known. In the one-component development method, generally, toner is charged by passing toner through a regulating portion formed by a toner carrier and a regulation plate pressed against the toner carrier, and a desired toner thin layer can be obtained. Therefore, it is advantageous in terms of simplification, miniaturization, and cost reduction of the apparatus. On the other hand, the deterioration of the toner is likely to be promoted due to the strong stress of the regulating portion, and the charge acceptability of the toner is likely to be lowered. 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, causing problems such as fogging. As a result, the life of the developing device is shortened. End up.

  In comparison, 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 carrier, which is a charge imparting member for the toner, has a large surface area, it is relatively resistant to contamination by toner and external additives, and is advantageous in extending the service life.

  However, even when a two-component developer is used, the surface of the carrier is contaminated by toner and external additives, and the toner charge amount is reduced by long-term use, such as fogging and toner scattering. Problems arise and their lifetime is by no means sufficient, and a longer lifetime is desired.

  As a method for extending the life of a two-component developer, Patent Document 1 discloses that a carrier is supplied by supplying a small amount of carrier together with toner or by itself and discharging a deteriorated developer having reduced chargeability accordingly. Has been disclosed to suppress the increase in the deteriorated carrier ratio. In this apparatus, since the carrier is replaced, it is possible to suppress a decrease in toner charge amount due to carrier deterioration at a certain level, which is advantageous in extending the service life. However, there is a problem in terms of cost and environment because a mechanism for collecting the discharged carrier is necessary and the carrier becomes a consumable item. Further, it is necessary to repeat a predetermined amount of printing until the new and old ratio of the carrier is stabilized, and there is an aspect that it cannot be said that the initial characteristics are maintained and utilized.

On the other hand, Patent Document 2 discloses a two-component developer comprising a toner externally added with carrier and particles having a chargeability opposite to the toner charge polarity, and a developing method using the same. In the developing method of Patent Document 2, the reverse polarity charged particles are added for the purpose of acting as abrasives and spacer particles, and it is shown that the effect of removing the spent on the carrier surface is effective in suppressing deterioration. Further, the cleaning portion of the image carrier is effective for improving the cleaning property and polishing the image carrier. However, in the disclosed developing method, the consumption amount of the toner and the reverse polarity charged particles differs depending on the image area ratio, and particularly when the image area ratio is small, the consumption of the reverse polarity charged particles becomes excessive, and the carrier in the developing device There is a problem that the deterioration suppressing effect is lowered.
JP 59-1000047 A JP 2003-215855 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide a compact developing device capable of preventing deterioration of a carrier and maintaining the cleaning performance of an image carrier and forming a good image over a long period in a developing device using a two-component developer. And

  The inventor conducted extensive research and was able to solve the above problems with any of the configurations described below.

  The developing device according to claim 1 is a toner, a carrier, a reverse polarity particle having a particle size distribution having a peak particle size of 0.8 to 1.5 μm charged to a polarity opposite to the charged polarity of the toner, and a peak A developer containing particles having a particle size distribution with a particle size of 0.2 to 0.6 [mu] m, a developer tank that contains the developer, and a developer carrier that carries and conveys the developer on the surface And separation means for separating the reverse polarity particles from the developer on the developer carrier, and recovery means for collecting the reverse polarity particles separated by the separation means in the developer tank. It is what.

  The developing device according to claim 2 is a toner, a carrier, a reverse polarity particle having a particle size distribution with a peak particle size of 0.8 to 1.5 μm charged to a polarity opposite to the charged polarity of the toner, and a peak A developer containing particles having a particle size distribution with a particle size of 0.2 to 0.6 [mu] m, a developer tank that contains the developer, and a developer carrier that carries and conveys the developer on the surface And a toner carrier for separating the toner from the developer on the developer carrier.

  The developing device according to claim 3 is the developing device according to claim 1 or 2, wherein the reverse polarity particles and the particles having a particle size distribution with a peak particle size of 0.2 to 0.6 µm are the toner. It is characterized by being externally added.

  The developing device according to claim 4 is the developing device according to any one of claims 1 to 3, wherein the particles having a particle size distribution with a peak particle size of 0.2 to 0.6 μm are the toner. The particles are charged with a polarity opposite to the charged polarity.

  An image forming apparatus according to a fifth aspect is characterized in that the developing device according to any one of the first to fourth aspects is used to develop a latent image on a latent image carrier.

  In the present invention, since the consumption of the reverse polarity particles is suppressed, it is possible to reduce the influence of the fluctuation of the consumption amount of the reverse polarity particles depending on the image area ratio, and particularly when the image area ratio is low (toner consumption is low) It is possible to suppress excessive consumption. In addition, the opposite polarity particles can effectively compensate for the chargeability of the carrier, and as a result, the deterioration of the carrier can be suppressed over a long period of time. Therefore, the toner charge amount is effectively maintained for a long time even when images having a relatively small image area ratio are continuously formed.

  Furthermore, by using a developer containing particles having a particle size distribution according to the present invention, it is possible to efficiently recover the reverse polarity particles and to effectively suppress the deterioration of the carrier. Further, the cleaning performance of the image carrier can be maintained satisfactorily for a long time.

  Exemplary embodiments of the present invention will be described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified. Absent.

FIG. 1 is a schematic configuration diagram of a main part of an image forming apparatus according to a first embodiment of the present invention.
(Image forming device)
This image forming apparatus is a printer that performs image formation by transferring a toner image formed on an image carrier (photoconductor) 1 to a transfer medium P such as paper by an electrophotographic method. This image forming apparatus has an image carrier 1 for carrying an image. Around the image carrier 1, a charging means 3 for charging the image carrier 1 and a static on the image carrier 1 are provided. A developing device 2 that develops 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 rotate the image carrier 1. They are arranged in order along the direction A.

The image carrier 1 is charged by the charging means 3 and then exposed by an exposure means (not shown) at the position of point E in the drawing to form an electrostatic latent image on the surface thereof. The developing device 2 develops the electrostatic latent image into 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 its mechanical force. As the image carrier 1, the charging unit 3, the exposure unit, 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 in the drawing as the charging means, a charging device that is not in contact with the image carrier 1 may be used.
(Developer)
In the present embodiment, the developing device 2 includes a developer tank 16 that contains the developer 24, a developer carrier 11 that carries the developer 24 supplied from the developer tank on the surface thereof, and the developer carrier. A reverse polarity particle recovery member 22 is provided as a separating means for separating toner or reverse polarity particles from the developer on the body, and the separated reverse polarity particles are recovered in the developer tank 16. Thereby, since consumption of reverse polarity particles can be suppressed, the reverse polarity particles can effectively compensate for the chargeability of carriers, and as a result, deterioration of carriers can be suppressed over a long period of time.
(Developer carrier)
The developer carrying member 11 includes a magnet roller 13 that is fixedly arranged, and a rotatable sleeve roller 12 that contains the magnet roller 13. The magnet roller 13 has five magnetic poles N1, S1, N3, N2, and S2 along the rotation direction B of the sleeve roller 12. Of these magnetic poles, the main magnetic pole N1 is disposed at the position of the developing region 6 facing the image carrier 1 and generates a repulsive magnetic field for peeling off the developer 24 on the sleeve roller 12. The pole portions N3 and N2 are arranged at positions facing the inside of the developing tank 16.
(Explanation of developer tank)
The developer tank 16 is formed of a casing 18 and normally contains a bucket roller 17 for supplying developer to the developer carrier 11 therein. An ATDC (Automatic Toner Density Control) sensor 20 for detecting toner concentration is preferably disposed at a position facing the bucket roller 17 of the casing 18.
(Toner supply part)
The developing device 2 normally has a replenishment section 7 for replenishing toner in the developer tank 16 for the amount of toner consumed in the development area 6 and a developer thin film for regulating the amount of developer on the developer carrier 11. It has a regulating member (regulating blade) 15 for stratification. The supply unit 7 includes a hopper 21 that stores supply toner 23 and a supply roller 19 for supplying toner into the developer tank 16.
(Separation means, recovery means)
In the developing device 2, as a separating unit that separates the reverse polarity particles from the developer on the developer carrier 11, a reverse made of a voltage-applicable material that separates the reverse polarity particles from the developer on the developer carrier 11. A polar particle recovery member 22 is employed. As shown in FIG. 1, the reverse polarity particle recovery member 22 is provided on the upstream side in the developer movement direction from the development region 6 in the developer carrier 11, and the developer is applied by applying a reverse polarity particle separation bias. The reverse polarity particles therein are electrically separated and collected on the surface of the reverse polarity particle recovery member 22. After the reverse polarity particles are separated by the reverse polarity particle recovery member 22, the remaining developer on the developer carrier 11, that is, the toner and the carrier are continuously conveyed, and the electrostatic latent image on the image carrier 1 is developed in the development region 6. Develop the image.

  The reverse polarity particle recovery member 22 is connected to a power source (not shown), and a predetermined reverse polarity particle separation bias is applied, whereby the reverse polarity particles in the developer are electrically separated on the surface of the reverse polarity particle recovery member 22.・ It is collected.

  The reverse polarity particle separation bias applied to the reverse polarity particle recovery member 22 varies depending on the charged polarity of the reverse polarity particles. That is, when the toner is negatively charged and the reverse polarity particles are positively charged, the average voltage is lower than the average value of the voltage applied to the developer carrier, and the toner is positively charged and the reverse polarity particles are Is negatively charged, the average voltage is higher than the average voltage applied to the developer carrying member. The difference between the average voltage applied to the reverse polarity particle recovery member and the average voltage applied to the developer carrier is 20 to 500 V, even when the reverse polarity particles are charged to either positive or negative polarity. In particular, 50 to 300V is preferable. If the potential difference is too small, it will be difficult to sufficiently collect the reverse polarity particles. On the other hand, if the potential difference is too large, the carriers held by the magnetic force on the developer carrier are separated by the electric field, and the original developing function may be impaired in the developing region.

In the developing device 2, it is further preferable that an alternating electric field is formed between the reverse polarity particle collecting member and the developer carrier. Since the toner reciprocates due to the formation of the AC electric field, the reverse polarity particles adhering to the toner surface can be effectively separated, and the recovery of the reverse polarity particles can be improved. At that time, an electric field of 2.5 × 10 ⁶ V / m or more is preferably formed. By forming an electric field of 2.5 × 10 ⁶ V / m or more, it becomes possible to separate the reverse polarity particles from the toner even by the electric field, and it is possible to further improve the reverse polarity separation and recovery. It becomes possible.

  In this specification, the electric field formed between the reverse polarity particle recovery member and the developer carrier is referred to as a reverse polarity particle separation electric field. Such a reverse polarity particle separation electric field is usually obtained by applying an AC voltage to one or both of the reverse polarity particle recovery member and the developer carrier. In particular, when an AC voltage is applied to the developer carrier to develop the electrostatic latent image with toner, an AC voltage applied to the developer carrier can be used to form a reverse polarity particle separation electric field. desirable. At this time, the reverse polarity particle separation electric field may have a maximum absolute value within the above range.

  For example, when the charge polarity of the reverse polarity particles is positive, the DC voltage and the AC voltage are applied to the developer carrier, and only the DC voltage is applied to the reverse polarity particle recovery member, the reverse polarity particle recovery member Only a DC voltage lower than the average value of the voltages (DC + AC) applied to the developer carrier is applied. Further, for example, when the charged polarity of the reverse polarity particles is negative, a DC voltage and an AC voltage are applied to the developer carrier, and only a DC voltage is applied to the reverse polarity particle recovery member, the reverse polarity particle recovery member Only a DC voltage higher than the average value of the voltages (DC + AC) applied to the developer carrier is applied. In these cases, the maximum absolute value of the reverse polarity particle recovery electric field is the maximum potential difference between the voltage applied to the developer carrier (DC + AC) and the voltage applied to the reverse polarity particle recovery member (DC). The value is a value obtained by dividing the value by the closest gap between the reverse polarity particle recovery member and the developer carrier, and it is desirable that the value be in the above range.

  Further, for example, when the charged polarity of the reverse polarity particles is positive, only the DC voltage is applied to the developer carrier, and the AC voltage and the DC voltage are applied to the reverse polarity particle recovery member, the reverse polarity particle recovery member A DC voltage on which an AC voltage is superimposed is applied so that the average voltage is lower than the DC voltage applied to the developer carrier. Also, for example, when the charged polarity of the reverse polarity particles is negative, only the DC voltage is applied to the developer carrier, and the AC voltage and DC voltage are applied to the reverse polarity particle recovery member, the reverse polarity particle recovery member A DC voltage on which an AC voltage is superimposed is applied so that the average voltage is higher than the DC voltage applied to the developer carrier. At these times, the maximum absolute value of the reverse polarity particle recovery electric field is the maximum potential difference between the voltage applied to the developer carrying member (DC) and the voltage applied to the reverse polarity particle recovery member (DC + AC). The value is a value obtained by dividing the value by the closest gap between the reverse polarity particle recovery member and the developer carrier, and it is desirable that the value be in the above range.

  Also, for example, when the charged polarity of the reverse polarity particles is positive and a DC voltage with an AC voltage superimposed on both the developer carrier and the reverse polarity particle recovery member is applied, the reverse polarity particle recovery member is loaded with the developer. A voltage (DC + AC) having an average voltage smaller than the average value of the voltage (DC + AC) applied to the body is applied. In addition, for example, when the polarity of the reverse polarity particles is negative and a DC voltage in which an AC voltage is superimposed on both the developer carrier and the reverse polarity particle recovery member is applied, the reverse polarity particle recovery member is loaded with the developer. A voltage (DC + AC) having an average voltage larger than the average value of the voltage (DC + AC) applied to the body is applied. At these times, the voltage applied to the developer carrier (direct current + alternating current) caused by the difference in the amplitude, phase, frequency, duty ratio, etc. of the alternating voltage component applied to each is applied to the reverse polarity particle recovery member. The value obtained by dividing the maximum value of the potential difference from the voltage (direct current + alternating current) by the closest gap between the reverse polarity particle recovery member and the developer carrier is the maximum absolute value of the reverse polarity particle recovery electric field, It is desirable that the value falls within the above range.

  The reverse polarity particles on the surface of the member separated and collected by the reverse polarity particle recovery member 22 are recovered in the developer tank 16 by the recovery means. As a recovery means for recovering the reverse polarity particles from the reverse polarity particle recovery member to the developer tank, the relationship between the average value of the voltage applied to the reverse polarity particle recovery member and the average value of the voltage applied to the developer carrier Can be reversed, and can be performed at the time of non-image formation, such as between pages during image formation before continuous image formation or after the start of image formation.

  The reverse polarity particle recovery member 22 may be made of any material as long as the voltage can be applied. For example, an aluminum roller subjected to a surface treatment may be used. 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.

  In FIG. 1, the reverse polarity particle recovery member 22 is provided separately from the restriction member 15 and the casing 26, but the reverse polarity particle recovery member may also serve as the restriction member 15 and the casing 26. That is, the regulating member 15 and the casing 26 may be used as the reverse polarity particle collecting member. In that case, a reverse polarity particle separation bias may be applied to the regulating member 15 and the casing 26. Thereby, space saving and low cost can be realized.

  If the developing device does not have the above separating means, the carrier deterioration suppressing effect in the developing device is lowered particularly when the image area ratio is small. The mechanism is considered to be based on the following mechanism. In a two-component developing device, a strong electric field is formed by applying an oscillating electric field or the like in the developing region, thereby improving toner separation from the carrier in the developer and improving development efficiency. When the developer containing the carrier is used, the carrier, toner, and reverse polarity particles are separated, and the carrier remains on the developer carrier by the magnetic attraction force, but the toner remains on the image portion of the electrostatic latent image. Are consumed in each non-image part. Therefore, the consumption balance between the toner and the reverse polarity particles is not stable depending on the image area ratio, and particularly when a large amount of images having a large background area are printed, the reverse polarity particles in the developer are preferentially consumed, It is considered that the chargeability cannot be compensated and the effect of suppressing carrier deterioration is reduced.

  In the present embodiment, the developer 24 includes toner, a carrier for charging the toner, and reverse polarity particles. The reverse polarity particles can be charged with a polarity opposite to the charging polarity of the toner by the carrier used. For example, when the toner is negatively charged by the carrier, the opposite polarity particles are positively charged particles that are positively charged in the developer. Also, for example, when the toner is positively charged by the carrier, the reverse polarity particles are negatively charged particles that are negatively charged in the developer. By containing reverse polarity particles in the two-component developer and suppressing the consumption of the reverse polarity particles to the photoreceptor side by the separating means, and accumulating the reverse polarity particles in the developer with durability, toner or Even if the chargeability of the carrier decreases due to the spent of the post-treatment agent on the carrier, the reverse polarity particles can charge the toner to the normal polarity, so that the chargeability of the carrier can be effectively compensated. Deterioration can be suppressed. The effect of suppressing the carrier deterioration by the reverse polarity particles is such that the particle size distribution of the reverse polarity particles has a peak in the range of 0.8 μm or more and 1.5 μm or less. By setting it in such a range, embedding of the reverse polarity particles in the toner can be suppressed, and the toner and the reverse polarity particles can be easily separated by the separating means. Can be performed efficiently. As a result, carrier deterioration can be effectively suppressed.

  However, the developer containing only the reverse polarity particles having the particle size distribution has an effect of suppressing carrier deterioration, but has a problem that the cleaning performance of the photosensitive member is lowered. This is because most of the particles having a smaller particle size of 0.8 μm or less among the reverse polarity particles are separated by the separating means and collected in the developing tank, so that the fluidity of the toner is lowered and the cleaning failure is caused. It is thought that it occurred.

Therefore, the developer 24 in this embodiment further includes particles having a peak in the particle size distribution of 0.2 μm or more and 0.6 μm or less so that the small diameter particles are transferred to the photoreceptor side. More preferably, the charged polarity of the particles is preferably opposite to that of the toner. By doing so, it is possible to suppress carrier deterioration, maintain the cleaning performance of the photoreceptor, and form a good image over a long period of time.
(Reverse polarity particles)
The reverse polarity particles used in the present invention 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 reverse polarity particles. For example, inorganic fine particles such as strontium titanate, barium titanate, and alumina, acrylic resin, benzoguanamine resin, and nylon resin are used. Fine particles composed of thermoplastic resin such as polyimide resin and polyamide resin or thermosetting resin can be used, and a positive charge control agent imparting positive charge property can be contained in the resin, or a nitrogen-containing monomer You may make it comprise the copolymer of these. Here, as the positive charge control agent, for example, a nigrosine dye, a quaternary ammonium salt, or the like can be used, and as the nitrogen-containing monomer, 2-dimethylaminoethyl acrylate, 2-acrylic acid 2- Diethylaminoethyl, 2-dimethylaminoethyl methacrylate, 2-diethylaminoethyl methacrylate, vinyl pyridine, N-vinyl carbazole, vinyl imidazole 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 thermoplastic resins such as thermoplastic resins or thermosetting resins can be used, and a negative charge control agent that imparts negative chargeability to the resin can be contained, or fluorine-containing acrylic monomers and fluorine-containing methacrylates can be used. You may make it comprise the copolymer of a system monomer. Here, as said negative charge control agent, a salicylic acid type, a naphthol type chromium complex, an aluminum complex, an iron complex, a zinc complex etc. can be used, for example.

  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.

If it is difficult to have two peaks of 0.2 to 0.6 μm and 0.8 to 1.5 μm with a single material, two types of materials may be used. In this case, as the 0.2 to 0.6 μm particles, metal oxide particles such as titanium oxide, zinc oxide, and silica can be used in addition to the materials mentioned as the reverse polarity particles. In addition, when two types of materials are used, the polarity of the toner particles having a peak at 0.2 to 0.6 μm may be any polarity, but the polarity is opposite to that of the toner in terms of the decrease in charge amount during durability. Is preferred. The cause is presumed to be that when the carrier surface is spent, the chargeability of the carrier is slightly reduced.
(toner)
The toner used in the present invention is not particularly limited, and a commonly used known toner can be used. A colorant in the binder resin and, if necessary, a charge control agent, a release agent, etc. It is possible to use those which are contained and treated with external additives. The toner particle diameter is not limited to this, but is preferably about 3 to 15 μm.

  In manufacturing such a toner, it can be manufactured by a publicly known method, for example, 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, or the like can be used, and it is generally preferable to use 2 to 20 parts by mass with respect to 100 parts by mass of 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 at a ratio of 0.1 to 10 parts by mass with respect to 100 parts by mass of 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 parts by mass with respect to 100 parts by mass of 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 a resin that has been hydrophobized with a silane coupling agent, a titanium coupling agent, silicon oil, or the like. Such a fluidizing agent is added at a ratio of 0.1 to 5 parts by mass with respect to 100 parts by mass of the toner.
(Career)
The carrier used in the present invention is not particularly limited, and a known carrier that is generally used can be used, and a binder type carrier, a coat type carrier, and the like can be used. Although it is not limited to this as a carrier particle size, 15-100 micrometers is preferable.

  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. Charging characteristics such as 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 for 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 in an amount of 50 to 90% by mass in the magnetic resin carrier.

  Silicone resin, acrylic resin, epoxy resin, fluorine resin, etc. are used as the surface coating material of the coat type carrier, and these resins are coated on the surface and cured to form a coat 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 / thermally. Is applied 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 copolymers, acrylic resins, 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, a surface treatment or 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, similarly to a binder-type carrier, positive or negatively chargeable fine particles are fixed to 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.
(Developer preparation)
The mixing ratio of the toner and the carrier may be adjusted so as to obtain a desired toner charge amount. The toner ratio is 3 to 50% by mass, preferably 6 to 30% by mass with respect to the total amount of the toner and the carrier. ing.

  The amount of the reverse polarity particles contained in the developer is not particularly limited as long as the object of the present invention is achieved, and is, for example, 0.1 to 5.0% by mass, particularly 0.5 to 3.0% with respect to the toner. Mass% is preferred.

  Further, the amount of particles having an average particle diameter peak in the developer of 0.2 to 0.6 μm is not particularly limited as long as the object of the present invention is achieved. -5.0 mass%, 0.1-2.0 mass% is especially preferable.

The developer is preferably adjusted by externally adding reverse polarity particles to the toner in advance and then mixing with a carrier.
(External supply processing of replenishment toner)
As the replenishment toner 23, it is desirable to use a toner having externally treated reverse polarity particles. By using toner with externally added reverse polarity particles and particles having a particle size distribution peak of 0.2 to 0.6 μm, it effectively assists in reducing the chargeability of the carrier, which gradually deteriorates with durability, and photosensitive. The body cleaning performance can be kept good. The external addition amount of the reverse polarity particles in the replenishing toner 23 is preferably 0.1 to 5.0% by mass, particularly preferably 0.5 to 3.0% by mass with respect to the toner. Further, the external addition amount of particles having a particle size distribution peak at 0.2 to 0.6 μm in the replenishing toner 23 is 0.01 to 5.0% by mass, particularly 0.1 to 2.0% by mass with respect to the toner. % Is preferred.
(Explanation of the operation of the developing device-developer movement I)
Specifically, in the developing device 2 shown in FIG. 1, the developer 24 in the developer tank 16 is mixed and agitated by the rotation of the bucket roller 17, frictionally charged, and then pumped up by the bucket roller 17 to be surfaced on the developer carrier 11. To the sleeve roller 12. The developer 24 is held on the surface side of the sleeve roller 12 by the magnetic force of the magnet roller 13 inside the developer carrying member (developing roller) 11, rotates together with the sleeve roller 12, and is provided to face the developing roller 11. The passing amount is regulated by the regulated member 15. Thereafter, only the reverse polarity particles contained in the developer are separated and collected by the reverse polarity particle recovery member at the portion facing the reverse polarity particle recovery member 22 as described above. The remaining developer from which the reverse polarity particles have been separated is conveyed to a developing area 6 facing the image carrier 1. In the developing region 6, developer spikes are formed by the magnetic force of the main magnetic pole N <b> 1 of the magnet roller 13, and are formed between the electrostatic latent image on the image carrier 1 and the developing roller 11 to which a developing bias is applied. Due to the force applied to the toner by the electric field, the toner in the developer moves toward the electrostatic latent image on the image carrier 1, and the electrostatic latent image is developed into a visible image. The development method may be a reversal development method or a regular development method. The developer 24 that has consumed toner in the developing region 6 is conveyed toward the developer tank 16 and is applied to the developer carrier 11 by the repulsive magnetic fields of the magnet roller equipolar portions N3 and N2 provided facing the bucket roller 17. It is peeled off from above and collected into the developer tank 16. When a supply control unit (not shown) provided in the supply unit 7 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 ensuring image density, the toner supply is performed. A drive start signal is sent to the drive means of the roller 19. Then, the toner replenishing roller 19 starts rotating, and with this rotation, the replenishing toner 23 stored in the hopper 21 is supplied into the developer tank 16. On the other hand, the reverse polarity particles collected by the reverse polarity particle recovery member 22 are returned onto the development roller by reversing the direction of the electric field applied to the developing roller and the reverse polarity particle recovery member during non-image formation. As the roller rotates, it is transported together with the developer and returned to the developer tank.

  Next, the main part of the image forming apparatus according to the second embodiment of the present invention is shown in FIG.

In FIG. 2, members having the same functions as those in FIG. 1 are denoted by the same reference numerals as those in FIG.
(Toner carrier)
The developing device 2 shown in FIG. 2 uses a developer carrier as a separating means for separating toner or reverse polarity particles from the developer on the developer carrier 11 instead of the reverse polarity particle recovery member 22 shown in FIG. A toner carrier 25 that separates the toner from the developer on 11 is employed. As shown in FIG. 2, the toner carrier 25 is provided between the developer carrier 11 and the image carrier 1, and a toner separation bias is applied to electrically remove the toner in the developer. It is designed to be separated and carried on the surface of the carrier. The toner separated and carried by the toner carrier 25 is conveyed by the toner carrier 25 and develops the electrostatic latent image on the image carrier 1 in the developing area 6.

  Thus, unlike the embodiment shown in FIG. 1, the developing device 2 does not separate the reverse polarity particles from the developer, but separates and carries the toner from the developer by the toner carrier 25. The toner separated and carried on the toner carrier 25 is used for developing the electrostatic latent image on the image carrier 1.

  The toner carrier 25 is connected to a power source (not shown), and a predetermined toner separation bias is applied, whereby the toner in the developer is electrically separated and carried on the surface of the toner carrier 25.

  The toner separation bias applied to the toner carrier 25 varies depending on the charging polarity of the toner, that is, when the toner is negatively charged, the average voltage is higher than the average value of the voltage applied to the developer carrier, When the toner is positively charged, the average voltage is lower than the average value of the voltage applied to the developer carrying member. Even when the toner is charged to either positive or negative polarity, the difference between the average voltage applied to the toner carrier and the average voltage applied to the developer carrier is 20 to 500 V, particularly 50 to It is preferable that it is 300V. If the potential difference is too small, the toner supply amount on the toner carrier is small, and a sufficient image density cannot be obtained. On the other hand, if the potential difference is too large, the toner supply becomes excessive and there is a risk that wasteful toner consumption will increase.

In the developing device 2, it is preferable that an alternating electric field is further formed between the toner carrier and the developer carrier. By forming an alternating electric field, the toner reciprocally vibrates, so that the toner and the reverse polarity particles can be effectively separated. At that time, an electric field of 2.5 × 10 ⁶ V / m or more is preferably formed. By forming an electric field of 2.5 × 10 ⁶ V / m or more, it becomes possible to separate the reverse polarity particles from the toner even by the electric field, and it becomes possible to further improve the toner separation property. .

  In this specification, the electric field formed between the toner carrier and the developer carrier is referred to as a toner separation electric field. Such a toner separation electric field is usually obtained by applying an AC voltage to one or both of the toner carrier and the developer carrier. In particular, when an AC voltage is applied to the toner carrier to develop the electrostatic latent image with toner, it is desirable to form a toner separation electric field using the AC voltage applied to the toner carrier. At this time, the maximum value of the absolute value of the toner separation electric field may be within the above range.

  For example, when the charging polarity of the toner is positive, a DC voltage and an AC voltage are applied to the developer carrier, and only a DC voltage is applied to the toner carrier, the toner carrier is loaded with the developer carrier. Only a DC voltage lower than the average value of applied voltages (DC + AC) is applied. Further, for example, when the charging polarity of the toner is negative, a DC voltage and an AC voltage are applied to the developer carrier, and only a DC voltage is applied to the toner carrier, the developer carrier is applied to the toner carrier. Only a DC voltage higher than the average value of the voltages (DC + AC) applied to is applied. In these cases, the maximum value of the absolute value of the toner separation electric field is the maximum value of the potential difference between the voltage (DC + AC) applied to the developer carrier and the voltage (DC) applied to the toner carrier. It is a value divided by the closest gap between the carrier and the developer carrier, and it is desirable that this value is in the above range.

  Also, for example, when the charging polarity of the toner is positive, only a DC voltage is applied to the developer carrier, and an AC electric field and a DC voltage are applied to the toner carrier, the developer carrier is applied to the toner carrier. A DC voltage on which an AC electric field is superimposed is applied so that the average voltage is lower than the DC voltage applied to. Also, for example, when the charging polarity of the toner is negative, only a DC voltage is applied to the developer carrier, and an AC electric field and a DC voltage are applied to the toner carrier, the developer carrier is applied to the toner carrier. A DC voltage on which an AC electric field is superimposed is applied so that the average voltage is higher than the DC voltage applied to. In these cases, the maximum value of the absolute value of the toner separation electric field is the maximum value of the potential difference between the voltage (DC) applied to the developer carrier and the voltage (DC + AC) applied to the toner carrier. It is a value divided by the closest gap between the carrier and the developer carrier, and it is desirable that this value is in the above range.

  In addition, for example, when the charging polarity of the toner is positive and a DC voltage in which an AC voltage is superimposed on both the developer carrier and the toner carrier is applied, the voltage applied to the developer carrier is applied to the toner carrier. A voltage (DC + AC) having an average voltage smaller than the average value of (DC + AC) is applied. In addition, for example, when the charging polarity of the toner is negative and a DC voltage in which an AC voltage is superimposed on both the developer carrier and the toner carrier is applied, the voltage applied to the developer carrier is applied to the toner carrier. A voltage (DC + AC) having an average voltage larger than the average value of (DC + AC) is applied. At these times, the voltage applied to the developer carrier (DC + AC) and the voltage applied to the toner carrier, which are caused by differences in the amplitude, phase, frequency, duty ratio, etc. of the AC voltage components applied to the respective components. A value obtained by dividing the maximum value of the potential difference from (DC + AC) by the closest gap between the toner carrier and the developer carrier is the maximum absolute value of the toner separation electric field, and this value is within the above range. It is desirable to do.

  The remaining developer on the developer carrier 11 from which the toner has been separated by the toner carrier 25, that is, the carrier and the reverse polarity particles, are conveyed by the developer carrier 11 as they are and are collected in the developer tank 16. In this embodiment, after separation of the toner, the reverse polarity particles are recovered as they are into the developer tank by the developer carrier 11, so that the reverse polarity collected by the reverse polarity particle recovery member described in the embodiment of FIG. The step of returning the polar particles to the developer tank at the time of non-image formation can be omitted.

The toner carrier 25 may be made of any material as long as the voltage can be applied. For example, an aluminum roller subjected to surface treatment may be used. 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.
(Explanation of Development Device Operation-Developer Movement II)
Specifically, in the developing device 2 shown in FIG. 2, the developer 24 in the developer tank 16 is mixed and agitated by the rotation of the bucket roller 17 and frictionally charged, and then pumped up by the bucket roller 17 as in the developing device 2. Then, it is supplied to the sleeve roller 12 on the surface of the developer carrier 11. The developer 24 is held on the surface side of the sleeve roller 12 by the magnetic force of the magnet roller 13 inside the developer carrying member (developing roller) 11, rotates together with the sleeve roller 12, and is provided to face the developing roller 11. The passing amount is regulated by the regulated member 15. Thereafter, only the toner contained in the developer is separated and carried on the toner carrier 25 at the portion facing the toner carrier 25 as described above. The separated toner is conveyed to a developing area 6 facing the image carrier 1. In the developing area 6, the toner on the toner carrier 25 is imaged by the force applied to the toner by the electric field formed between the electrostatic latent image on the image carrier 1 and the toner carrier 25 to which the developing bias is applied. It moves toward the electrostatic latent image on the carrier 1, and the electrostatic latent image is developed into a visible image. The development method may be a reversal development method or a regular development method. The toner layer on the toner carrying member that has passed through the developing region 6 is transported to the developing region through toner supply / recovery by a magnetic brush at the facing portion between the toner carrying member and the developer carrying member. On the other hand, the developer separated from the toner and remaining on the developer carrying member 11 is conveyed to the developer tank 16 as it is, and is supplied to the magnet roller equipolar portions N3 and N2 provided facing the bucket roller 17. It is peeled off from the developer carrier 11 by the repulsive magnetic field and collected into the developer tank 16. When a supply control unit (not shown) provided in the supply unit 7 detects that the toner concentration in the developer 24 has become equal to or lower than the minimum toner concentration for securing the image density, as in FIG. A drive start signal is sent to the driving means of the roller 19, and the replenishment toner 23 is supplied into the developer tank 16.

(1) Developing device and setting conditions The developing device A and the developing device B shown below were used as the developing device.

Developing device A: The developing device shown in FIG. 1 was used, and a developing wave of a rectangular wave having an amplitude of 1.4 kV, a DC component of −400 V, a duty ratio of 50%, and a frequency of 2 kHz was applied to the developer carrying member. A DC bias of −550 V, which is a potential difference of −150 V with respect to the average potential of the developing bias and a potential difference of 850 V with respect to the maximum potential of the developing bias, was applied to the reverse polarity particle recovery member. As the reverse polarity particle recovery member, an aluminum roller having an alumite treatment on the surface was used, and the gap at the closest part between the developer carrying member and the reverse polarity particle recovery member was set to 0.3 mm. The background potential of the electrostatic latent image formed on the image bearing member was −550V, and the image portion potential was −60V. The gap at the closest part between the image carrier and the developer carrier was 0.35 mm. The maximum absolute value of the reverse polarity particle separation electric field formed between the reverse polarity particle recovery member and the developer carrying member was 850 V / 0.3 mm = 2.8 × 10 ⁶ V / m. Recovery of the reverse polarity particles collected by the reverse polarity particle recovery member into the developer tank was performed by reversing the voltage applied to the developer carrier and the reverse polarity particle recovery member at the timing between the sheets.

Developing device B: The developing device shown in FIG. 2 was used, and a DC voltage of −400 V was applied to the developer carrying member. A rectangular wave developing bias having an amplitude of 1.6 kV, a DC component of −300 V, a duty ratio of 50%, and a frequency of 2 kHz was applied to the toner carrier. The average potential of the toner carrier has a potential difference of 100V with respect to the potential of the developer carrier, and the maximum potential difference is 900V. An aluminum roller having an alumite treatment on the surface was used for the toner carrier, and the gap at the closest part between the developer carrier and the toner carrier was 0.3 mm. The background potential of the electrostatic latent image formed on the image carrier is −550 V, the image part potential is −60 V, and the gap between the image carrier and the toner carrier is 0.15 mm. The maximum value of the absolute value of the toner separation electric field formed between the toner carrier and the developer carrier was 900 V / 0.3 mm = 3.0 × 10 ⁶ V / m.
(2) Preparation of developer As a developer, a carrier for bizhub C350 (particle size: about 33 μm) manufactured by Konica Minolta and a toner obtained by externally adding the following various particles, a toner ratio of 8% by mass in the developer is used. Using. The toner ratio is the ratio of the total amount of toner and post-treatment agent to the total amount of developer.
(3) Preparation of toner sample As the toner, a negatively charged toner having a particle diameter of about 6.5 μm produced by a wet granulation method was used. With respect to 100 parts by mass of the toner base material, external additive particles (first particles, second particles, and third particles) as a fluidizing agent are added to the Henschel as the first external addition treatment under the conditions shown in Table 1. After processing using a mixer (made by Mitsui Mining & Mining Co., Ltd.), as a second external addition treatment, particles 1 and particles 2 containing opposite polarity particles were processed using a Henschel mixer (made by Mitsui Mining & Mining Co., Ltd.). . In the table, the charged particles having a negative polarity are particles having the same polarity as the toner.

  The hydrophobic silica used here is obtained by subjecting silica to surface treatment with hexamethyldisilazane (HMDS) which is a hydrophobizing agent. Further, the hydrophobic titanium oxide in the first external addition treatment is a surface treatment of anatase-type titanium oxide with isobutyltrimethoxysilane as a hydrophobizing agent in an aqueous wet process, and particles in the second external addition treatment Hydrophobic titanium oxide No. 1 is obtained by subjecting anatase-type titanium oxide to surface treatment with isobutyltrimethoxysilane which is a hydrophobizing agent in an aqueous wet process. In addition, the hydrophobic titanium oxide of the particles 2 in the second external addition treatment is obtained by surface-treating anatase-type titanium oxide with aminosilane as a hydrophobizing agent in an aqueous wet process. In addition, about the crushing process, it performed for 5 minutes at 50 m / s using the Henschel mixer.

  The particle size distribution measurement results of the external additives of Samples 1 to 8 and Comparative Samples 2 to 14 are shown in FIGS. Table 1 shows the peak value of the particle size distribution of each sample and the comparative sample.

  Here, the second peak value represents the peak value of the opposite polarity particles. This can also be said from the fact that the second peak hardly appears when the particle size distribution of the external additive after separating the particles of opposite polarity from the developer is measured.

(Evaluation method of Examples and Comparative Examples)
Using the toner sample and the developing device shown in Table 2, the Konica Minolta copier bizhub C350 is mounted on a modified image forming apparatus, and an endurance evaluation of 50,000 sheets using an image chart with an image area ratio of about 5% (A4 The toner charge amount and cleaning quality of the developer after initial and after durability were evaluated.

  In any of the image forming apparatuses, the toner sample subjected to the external addition process described in each of Examples and Comparative Examples was used as the replenishing toner. Further, the developer sampling was performed from the developer tank. When the toner charge amount change is 4 μc / g or less in absolute value, “◯” indicates that the toner charge amount is 4 μc / g or more and 7 μc / g or less, and “Δ” indicates that the toner charge amount change exceeds 7 μc / g.

Regarding the evaluation of the cleaning quality of the photoconductor, a solid white image was printed, and a streak in the paper passing direction (black streaks due to unwiped toner) was evaluated in three stages. ○ indicates no black streak, Δ indicates a very slight black streak with no quality problem, and × indicates a black streak with some quality problem.
(Measurement method of toner charge)
The toner charge amount was measured using the apparatus shown in FIG. First, 1 g of developer measured with a precision balance is placed on the entire surface of the conductive sleeve (31) so as to be uniform. A voltage of 2 kV is supplied from the bias power source (33) to the sleeve (31), and the rotational speed of the magnet roll (32) provided in the conductive sleeve (31) is set to 1000 rpm. In this state, the toner is collected in the cylindrical electrode (34) by being left for 30 seconds. After 30 seconds, the potential Vm of the cylindrical electrode (34) was read, the charge amount of the toner was determined, and the mass of the collected toner was measured with a precision balance to determine the average charge amount.
(Measurement method of particle charge)
The particle charge amount in Table 1 was also measured by the apparatus shown in FIG.
Toner prepared by externally adding particles to be measured is mixed with a carrier to prepare a developer, and 1 g is placed on the conductive sleeve (31). The subsequent operation is the same as the toner charge amount measurement, but a bias voltage having a polarity for collecting only particles is applied to the cylindrical electrode (34). Note that particles having the same polarity as the toner cannot be measured.
(Measuring method of particle size distribution)
In the particle size distribution measurement of the external additive used in the present invention, 300 particle images were processed from the particle images obtained by a scanning electron microscope using Image-Pro manufactured by Planetron as image processing software. The particle size was determined and statistical processing was performed. The number of measurements may be 300 or more. As another method, the measurement may be performed using a laser scattering type particle size distribution measuring instrument, for example, SALD2200 (manufactured by Shimadzu Corporation).
(Evaluation results)
Table 2 also shows the toner charge amount after 50 k sheets of printing durability and the black stripe evaluation results after 50 k sheets in each example and comparative example.

  From these results, in the developing device configured to collect the reverse polarity particles shown in FIGS. 1 and 2, particles having a peak at 0.2 μm to 0.6 μm and reverse polarity particles having a peak at 0.8 μm to 1.5 μm It can be seen that by using a developer containing the toner, the toner charge amount does not decrease and the toner transition is stable, and the cleaning function is also improved, and stable quality can be ensured over a long period of time.

  In addition, since the charge amount tends to decrease slightly in Example 1 and Example 2, it can be seen that particles having a peak at 0.2 μm to 0.6 μm preferably have a charge polarity opposite to that of the toner.

1 is a schematic configuration diagram of a main part of an image forming apparatus according to a first embodiment of the present invention. FIG. 3 is a schematic configuration diagram of a main part of an image forming apparatus according to a second embodiment of the present invention. The schematic block diagram of the measuring device of the amount of charge is shown. The particle size distribution measurement result of the samples 1-4 is shown. The particle size distribution measurement result of samples 5-8 is shown. The particle size distribution measurement results of Comparative Samples 2 to 4 are shown. The particle size distribution measurement result of the comparative samples 5-7 is shown. The particle size distribution measurement results of Comparative Samples 8 to 10 are shown. The particle size distribution measurement result of the comparative samples 11-14 is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image carrier 2 Developing apparatus 3 Charging means 4 Transfer roller 5 Cleaning blade 6 Development area 7 Replenishment part 11 Developer carrier 12 Sleeve roller 13 Magnet roller 14 Magnet 15 Control member 16 Developer tank 17 Bucket roller 18 Casing 19 Supply roller 20 ATDC sensor 21 Hopper 22 Reverse polarity particle recovery member 23 Replenished toner 24 Developer 25 Toner carrier 31 Conductive sleeve 32 Magnet roll 33 Bias power supply 34 Cylindrical electrode

Claims (5)

Toner, carrier, reverse polarity particles charged with a polarity opposite to the charged polarity of the toner and having a particle size distribution with a peak particle size of 0.8-1.5 μm, and a peak particle size of 0.2-0. A developer comprising particles having a particle size distribution of 6 μm;
A developer tank containing the developer;
A developer carrying member carrying and carrying the developer on the surface;
Separating means for separating the opposite polarity particles from the developer on the developer carrying member;
Recovery means for recovering the reverse polarity particles separated by the separation means in the developer tank;
A developing device comprising: Toner, carrier, reverse polarity particles charged with a polarity opposite to the charged polarity of the toner and having a particle size distribution with a peak particle size of 0.8-1.5 μm, and a peak particle size of 0.2-0. A developer comprising particles having a particle size distribution of 6 μm;
A developer tank containing the developer;
A developer carrying member carrying and carrying the developer on the surface;
A toner carrier for separating the toner from the developer on the developer carrier;
A developing device comprising: The developing device according to claim 1, wherein the reverse polarity particles and the particles having a particle size distribution with a peak particle size of 0.2 to 0.6 μm are externally added to the toner. . 4. The particle according to claim 1, wherein the particle having a particle size distribution having a peak particle size of 0.2 to 0.6 [mu] m is a particle charged to a polarity opposite to the charging polarity of the toner. The developing device according to claim 1. An image forming apparatus that develops a latent image on a latent image carrier using the developing device according to claim 1.

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