JP4890099B2 - Developing device, process cartridge, and image forming apparatus - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a laser beam printer, and a fax machine, and a developing device and a process cartridge used therefor, and more particularly, an image forming apparatus for forming a color image and a process used therefor. The present invention relates to a cartridge and a developing device.

In recent years, copying machines, laser printers, and the like using electrophotography have made remarkable progress in various respects such as improvement in image quality and printing speed, and reduction in machine size.
The electrophotographic system uses a photoconductive substance to form an electrical latent image on a photoreceptor, a developing process for developing the latent image with toner, and recording the developed toner image on paper or the like. The image forming apparatus includes a transfer process for transferring to a medium and a fixing process for fixing the transferred toner image to a recording medium by heating using a fixing roller. This is a very important process for the enhancement of functions.
Generally, electrophotographic development methods include a one-component development method using only toner as a developer and a two-component development method using toner and carrier as a developer.

In the one-component development method, for example, toner is supplied to a developing roller as a developer carrying member, and the toner layer regulating member regulates the toner layer thickness, and at the same time frictionally charges to form a thin layer toner formed on the developing roller. Is supplied to the surface of the photoreceptor as a latent image carrier by an electric force to develop the electrostatic latent image. As described above, the one-component development method is to visualize the electrostatic latent image formed on the latent image carrier with toner in the development region where the developing roller and the latent image carrier are opposed to each other. However, in order to form a high-quality visible image having a predetermined density, it is necessary to supply a large amount of sufficiently charged toner.
On the other hand, in the two-component development system, the toner and the carrier are agitated to impart an appropriate charge amount to the toner, thereby developing. This system is a system in which a latent image is developed by transporting a developer to a latent image carrier by, for example, a developing roller provided with a nonmagnetic sleeve that can rotate on the outside of a magnet roller. In such a two-component development system, it is known that the carrier plays a role of charging and transporting the toner, and the mixing ratio and stirring state of the carrier greatly affect the image formation.
In both the one-component development method and the two-component development method, it is necessary to impart a desired charge amount to the toner by frictional charging and transport the toner to the development region.

In the development process, the characteristics of the toner itself are important in order to sufficiently charge and convey the toner. In particular, the fluidity is not only related to the conveyance of the toner, but also affects the uniformity of stirring and the frictional charging. Therefore, a high level of toner fluidity is required to increase the speed or size of copying machines, laser printers, and the like.
For example, in order to achieve high speed, it is necessary to stir and charge the toner in a short time. If the fluidity of the toner is low, the progress of frictional charging is inhibited, and the toner with a low charge amount is carried to the development area. Therefore, there is a risk that toner scattering and background staining may occur.
In the two-component development method, if the developer is not sufficiently stirred, the mixing ratio of the carrier and the toner becomes unstable, which causes the toner charge amount to become unstable. In the one-component development system, if the toner has low fluidity, a thin toner layer is not uniformly formed on the developing roller rotating at high speed, and the toner cannot be sufficiently charged by the toner regulating member. Cause scattering and dirt.

On the other hand, it is most effective to reduce the developer capacity in the developing device in order to reduce the size of the device. However, if the developer capacity is reduced, the toner in the developing device is newly replenished when the toner is replenished. It becomes difficult to mix the used toner in a short time. Further, in order to achieve miniaturization with the two-component developing system, the agitating screw must be miniaturized, which lowers the agitating ability. Therefore, in order to promote the downsizing of the apparatus, the fluidity of the toner is required more than ever.

Hereinafter, control of toner characteristics, particularly fluidity, by the external additive treatment will be described.
In general, as a method for improving toner characteristics, there are a method of adding a substance according to the purpose to a constituent material of the toner and a method of attaching fine particles according to the purpose to the toner surface.
As a method of adding a substance according to the purpose, for example, a method of adding a charge control agent such as a nigrosine dye or a modified product thereof, a triphenylmethane compound or an imidazole derivative to the inside of the toner for the purpose of controlling the chargeability of the toner. Can be mentioned. Such charge control agents include, for example, JP-B-1-54694, JP-B-1-54695, JP-A-51-455, JP-B-63-57787, JP-A-3-11964, It is disclosed in JP-A-3-202856.

On the other hand, as a method of attaching fine particles according to the purpose to the toner surface, a method of attaching inorganic oxide particles having a particle size of several to several hundreds of nanometers on the surface of toner particles is known.
Examples of the inorganic oxide particles include metal oxides such as silica, alumina, and titania obtained by a dry process or a wet process. These inorganic oxide particles may be used after their surfaces have been subjected to a hydrophobic treatment. Examples of the hydrophobizing agent include hexamethyldisilazane and silicon oil.
Thus, the method of attaching the fine particles to the toner surface has a great effect on improving the fluidity of the toner. As publicly known literatures relating to this method, for example, “Basics and Applications of Electrophotographic Technology, edited by Electrophotographic Society” (Corona) can be cited.
As another method for attaching fine particles according to the purpose to the toner surface, a method of adding a fatty acid metal salt such as zinc stearate or calcium stearate is known. Originally, in an electrophotographic apparatus, a fatty acid metal salt is applied to the surface of a photoreceptor in order to reduce the friction between the cleaning blade and the photoreceptor or to improve the transfer rate of toner from the photoreceptor to the intermediate transfer belt. Was done. In this case, for example, by attaching the fatty acid metal salt to the toner surface and applying the fatty acid metal salt to the surface of the photoreceptor using the toner as a medium, a dedicated device or member can be omitted.
Recently, it has been clarified that the fatty acid metal salt has an effect of improving the toner characteristics itself in addition to the above-described effects. For example, JP 2003-29446 A, JP 9-251214 A, etc. As described in the above, it has been found that there is an effect of preventing aggregation between the toners and improving the chargeability of the toner particles.

By the way, as technical problems of image forming apparatuses such as copying machines and printers, in addition to speeding up and downsizing of the apparatus, more stable image output performance has been demanded. It is sought after.
Specifically, the fluidity of the toner deteriorates over time by external additives such as inorganic particles being peeled off from the toner surface or embedded in the toner by rubbing when the toner is stirred and charged. There is a problem of doing. In other words, as the speed of developing machines increases and miniaturization progresses, a desired charge amount must be imparted to the toner in a short time, and the stress applied to the toner increases. It tends to happen. When the external additive is peeled off or buried, it becomes difficult to control the fluidity and charge amount of the toner, and image quality defects such as scumming and toner scattering are likely to occur. Various studies have been made so far on the technology for reducing the deterioration of the developer, but it is considered that the importance will increase more and more in the future.

As a conventional technique for preventing the deterioration of the developer, for example, Patent Document 1 discloses an apparatus developed for the purpose of suppressing the progress of deterioration of a two-component developer or a magnetic one-component developer, and is included in a magnet roller. Among the plurality of fixed magnets, the restricting magnet that is disposed closest to the doctor blade and has the restricting magnetic pole is disposed so as to be adjacent to the surface facing the developing sleeve surface and on the upstream side in the sleeve rotation direction. In addition, an image forming apparatus is disclosed in which a ridge corner with a surface facing an upstream side adjacent magnet, which is a magnet having an upstream side adjacent magnetic pole, is chamfered.
Further, Patent Document 2 discloses an apparatus developed for the purpose of smoothing the pumping of the developer and suppressing the driving torque of the screw and the stress of the developer, and is a lower part that conveys the developer in the axial direction. The upper screw is disposed above the lower screw and has an upper screw that conveys the developer in the axial direction, and the conveying capability of the upper screw in the pumping portion where the developer is pumped from the lower screw to the upper screw. However, a developing device is disclosed that is larger than the conveying capability of the lower screw in the portion.

JP 2005-017871 A Japanese Patent Laid-Open No. 11-024382

However, most of the conventional techniques for reducing the deterioration of the developer have been to reduce the mechanical stress on the toner including the reduction of the torque of the developing device. The reduction of the stress on the toner by such an approach is almost optimized by various technologies of each company, and it is considered that the life of the developing unit is approaching the limit.
The cause of the progress of toner deterioration is that for some reason, stress is applied to the toner, and the force causes the irreversible deformation of the surface of the toner, which is a polymer. It is done. That is, for the toner, the mechanical external load received from the agitating member, the layer regulating member, etc., the electrostatic adhesion generated when the toner itself is charged, and the non-electrostatic adhesion such as van der Waals force Can all cause degradation as well. When these three types of causes are compared, mechanical external load is the most dominant, so reducing this force has been the main study issue so far, but mechanical external load design In the present situation, it is matured so that it is difficult to reduce the deterioration of the toner.

In view of such circumstances, the present invention is a technique that can reduce toner deterioration by a method other than the optimization of mechanical external load design, more specifically, the time during which the toner is charged is as short as possible. Thus, a new technique for suppressing toner deterioration is provided. That is, an object of the present invention is to reduce toner deterioration over time due to peeling or embedding of an external additive, thereby suppressing image quality defects such as dirt and toner scattering and outputting a stable image over a long period of time. Another object of the present invention is to provide a developing device, a process cartridge, and an image forming apparatus using the same.

In order to achieve the above-mentioned object, the present inventor has made various studies on shortening the time during which the developer is charged, and the developer adheres to the surface of the developer-carrying member from the stirring charging unit that charges the developer. It has been found that by reducing the distance to the developer amount regulating portion that regulates the developer thickness or shortening the time, the toner stress is reduced and the deterioration thereof is reduced. Based on this knowledge, as a result of earnest research on the positional relationship between the members in the developing device, the stirring charging means functions as a developer supplying means for supplying the developer to the developer carrying member, and the stirring charging is performed. By providing the developer regulating means on the downstream side in the rotation direction of the developer carrying member adjacent to the means, it is possible to shorten the wasteful time that the developer is charged as much as possible, and to reduce the stress and hence the deterioration of the developer. And reached the present invention.
As described above, the present invention reduces the deterioration of the toner caused by the electrostatic adhesion between the carrier and the toner generated when the developer is charged, and attempts to reduce the mechanical external load on the developer. This is different from the conventional technology.

That is, the developing device according to the present invention includes a developer carrying member that develops an electrostatic latent image by supplying a developer to the image carrying member, and a developer that is supplied to the developer carrying member and has a developer on the surface thereof. Developer supplying means for forming the thin film, developer regulating means for regulating the thickness of the thin film developer, and stirring charging means for stirring and charging the developer supplied to the developer carrying member in advance. The stirring charging means functions also as the developer supply means, and the developer regulating means is arranged on the downstream side in the rotation direction of the developer carrier adjacent to the stirring charging means. development are al provided, at a position opposed to the image bearing member rotational direction downstream side surface than the portion facing the development area of in the developer carrying member, scraping the developer remaining on the developer carrying member The developer collecting means and the collected developer are And a toner supply means for replenishing toner in the transport path, and the developer collecting means on the upstream side in the rotation direction of the developer carrier. It is characterized in that a discharging means for discharging the developer collected by the developer collecting means is provided .
In this case, the casing of the developer agitation container that accommodates the agitation charging unit can be used as the developer regulating unit.
In addition, the transport path may have a cross-sectional area other than the inlet and outlet smaller than the cross-sectional area of the inlet and outlet.

The process cartridge according to the present invention is a process cartridge in which an image carrier and a developing device that develops an electrostatic latent image formed on the surface of the image carrier are integrated and detachably formed on the main body of the image forming apparatus. The developing device is any one of the developing devices described above.
The image forming apparatus according to the present invention includes an image carrier, a charging device that uniformly charges the surface of the image carrier, and an electrostatic latent image on the charged image carrier surface based on image information. An exposure device for forming, a developing device for supplying a developer to the electrostatic latent image to make a visible image, and a visible image formed on the surface of the image carrier directly or via an intermediate transfer member In the image forming apparatus including the transfer device, the developing device is any one of the developing devices described above or the developing device of the process cartridge.

According to the developing device of the present invention, since the time during which the developer is charged more than necessary is shortened, the electrostatic stress received by the developer is reduced, the deterioration is prevented, and the image is stable over a long period of time. Can be output.
According to the process cartridge of the present invention, even when the members are replaced, it is possible to eliminate gap deviation between the image carrier and the developer carrier, and for example, when a static eliminator, a scraper, etc. are provided. The positional relationship among them, the developer carrier and the image carrier is always kept constant, and good image quality can be formed over a long period of time.
According to the image forming apparatus of the present invention, the time from the start of charging of the developer to the development of the latent image is shortened, in other words, the unnecessary time in which the toner is electrically restricted is shortened. As a result, the stress applied to the toner is reduced, and the developer can be used stably over a long period of time to form a high-quality image.

First, in the present invention, the reason why the deterioration of the toner can be reduced by controlling the charging time of the developer, in other words, the time of receiving the electrostatic adhesive force will be described.
Various studies have been made on the measurement of electrostatic adhesion force and non-electrostatic adhesion force of toner. For example, in a study using a centrifuge (Ricoh Technical Report No. 26 (2000 edition) Study of toner adhesion, effect of external additives), electrostatic adhesion between toner and photoreceptor is several hundred nN. It is reported that it is an order. Although the adhesive force varies depending on the material, the adhesive force between the toner and the carrier is considered to be in the same order. At present, the toner particle size is typically about 5 μm, for example, and is considered to be in contact with the carrier at about several percent of the surface area. Therefore, the contact area of the toner with the carrier is on the order of 10 ⁻¹⁴ m ² . It is believed that there is.
That is, the force per unit area between the toner and the carrier is on the order of 100 × 10 ⁻⁹ / 10 ⁻¹⁴ = 10 ⁷ Pa = 10 MPa. On the other hand, the bending strength (yield strength) of the polymer is on the order of several tens of MPa (nylon: 70 MPa, polycarbonate: 60 MPa). Therefore, it can be seen that the toner is sufficiently deformed and deteriorates due to the electrostatic adhesion force.
This fact has been shown experimentally. That is, in Colloids and Surfaces A: Physicochemical and Engineering Aspects 87 (1994) 245-256, toner is attached to the tip of a cantilever which is a probe of an atomic force microscope, and the adhesion of the toner is evaluated. At that time, it has been reported that non-electrostatic adhesion increases when a load of several tens of nN is intentionally applied to the toner. This result shows that the toner is also deteriorated by the electrostatic adhesion which is on the order of several hundred nN.
From the above, it can be seen that optimization including electrostatic force is required in order to achieve a high level of stress reduction for toner.

As one method embodying the present invention, the toner agitation and charging means functions as a developer supplying means for supplying a developer to a developer carrying member (hereinafter referred to as a developing roller), and is supplied to the surface of the developing roller. Examples include a method in which developer regulating means for regulating the amount of developer is disposed adjacent to or integrated with the stirring charging means. In this method, for example, the amount of developer on the surface of the developing sleeve can be regulated by the size of the takeout port from which the developer is carried out from the stirring charging means, that is, the casing forming the takeout port. By reducing the distance or time from when the developer is supplied to the developing sleeve until the excess developer is removed by the regulating means until the thin layer of the predetermined thickness is formed, the developer stress is reduced overall. The deterioration can be suppressed.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention. In FIG. 1, an image forming apparatus 1 includes a photosensitive member 2 that rotates in the clockwise direction in the drawing, a charging device 3, a writing device 4, a developing device 5, a transfer device 6, and a blade that are sequentially arranged around the photosensitive member 2. The cleaning device 13 and the photosensitive member neutralizing device 8 provided with 13a, and a control device and a voltage applying device (not shown) are mainly configured. The image forming apparatus main body is accommodated in, for example, a housing not shown.
The image forming apparatus 1 is provided with a paper feeding cassette (not shown). The paper feed cassette is provided with a paper feed roller. The paper feed roller carries out the recording paper stored in the paper feed cassette one by one, adjusts the timing with a pair of registration rollers (not shown), and then transfers the recording paper. The toner is supplied to a transfer portion between the apparatus 6 and the photoreceptor 2.

Hereinafter, an operation of the image forming apparatus having such a configuration will be described.
First, the photosensitive member 2 as an image carrier is rotated in the clockwise direction in the drawing, and the surface of the photosensitive member 2 is uniformly charged by the charging device 3. An electrostatic latent image is formed on the surface of the photoconductor 2 by irradiating the surface of the photoconductor 2 with a laser beam, for example, which is modulated by the writing device 4 based on the image data. The developing device 5 supplies toner to the photoreceptor 2 on which the electrostatic latent image is formed, and the electrostatic latent image is developed to form a toner image.
The toner image on the surface of the photoreceptor 2 formed in this way is transferred by a transfer device 6 to a recording sheet (not shown) supplied between the photoreceptor 2 and the transfer device 6. The recording paper on which the toner image is transferred is conveyed to a fixing unit (not shown), and the toner image is fixed on the recording paper at a predetermined temperature or pressure. Thereafter, the recording paper on which the toner image is fixed is discharged onto a paper discharge tray (not shown).

On the other hand, the photoreceptor 2 after the toner image is transferred to the recording paper is further rotated, and the toner remaining on the surface of the photoreceptor 2 is scraped off by the blade 13a of the cleaning device 13. Next, the surface of the photoreceptor 2 from which the residual toner has been removed is neutralized by the neutralization device 8. The surface of the photoreceptor 2 that has been neutralized by the neutralization device 8 is uniformly charged by the charging device 3, and then the above-described steps are sequentially repeated to form a continuous image.
In the present embodiment, the cleaning device 13 scrapes off the residual toner on the photoconductor 2 with the blade 13a. However, instead of the blade 13a, the residual toner on the photoconductor 2 is scraped with a fur brush, for example. It may be dropped.

Below, the characteristic part of this invention is demonstrated in detail.
FIG. 2 is a diagram illustrating a schematic configuration of the developing device 5 of FIG. 1, which is a developing device according to the embodiment of the present invention. In FIG. 2, the developing device forms a process cartridge integrally with the photosensitive member 2.
That is, in the developing device 5, the developing sleeve 23 is integrally disposed so as to face the developing region of the photoreceptor 2. The developing sleeve 23 includes a magnet roll 22. An agitation charging member 30 for agitating and mixing the developer is disposed above the developing sleeve 23 in the figure. The agitation charging member 30 supplies the developer charged by agitation to the developing sleeve 23. Also works. The developing sleeve 23 and the stirring charging member 30 are covered with a casing 40, and an end portion of the casing 40 near the stirring charging member 30 is located at a position adjacent to the stirring charging member 30 with a predetermined interval from the surface of the developing sleeve 23. And functions as a regulating member that regulates the thickness of the developer deposited on the surface of the developing sleeve.

In the developing device 5 having such a configuration, the developer obtained by mixing the toner and the carrier is conveyed to the surface of the developing sleeve 23 while being stirred by the stirring charging member 30. At this time, the developer is charged to a charge necessary for developing the electrostatic latent image on the photoreceptor 2 while being stirred and conveyed by the action of the stirring and charging member 30.
The developer supplied onto the developing sleeve 23 is transported toward the developing area which is a position facing the photoconductor 2 along the rotation of the developing sleeve 23. At this time, the developer passes through a gap with the casing of the developer agitating container 34 as a restricting member, so that the amount of the developer is regulated and a thin layer of an amount necessary for image output is formed. The gap between the developer agitating container 34 and the developing sleeve 23 is determined by the amount of developer to be supplied to the developing sleeve, and is, for example, in the range of 0.1 to 2 mm. It is determined as appropriate based on the linear velocity of the developing sleeve 23, the diameter of the developing sleeve 23, the toner concentration in the developer, and the like. The thin-layer developer is transported to the developing area facing the photoreceptor 2 and is supplied onto the photoreceptor 2 due to a bias difference between the photoreceptor 2 and the developing sleeve 23 to develop the electrostatic latent image to produce a toner image. Form. At this time, a DC or DC + AC bias is applied to the developing sleeve 23 by a bias power supply (not shown).

  The developer remaining on the developing sleeve 23 after passing through the developing region of the photoreceptor 2 is conveyed again to the position of the stirring charging member 30. The toner concentration in the developer changed by being used for development is kept constant by the toner newly supplied from the hopper 31 as a toner supply container. At this time, the toner replenishment amount is controlled based on the detection value of a toner density sensor (not shown), and the optimum amount is always replenished. The toner replenishing method is not particularly limited. For example, the toner density can be made uniform by replenishing the toner little by little over the entire surface in the longitudinal direction.

According to the present embodiment, the developer agitation charging member 30 also functions as a developer supply device that supplies the developer to the developing sleeve 23, and at one end of the casing 34 so as to be adjacent to the agitation charging member 30. By providing the substitute developer regulating member 34a, the time from when the toner is charged until it is regulated to the required amount can be shortened, and the time during which a large amount of toner is electrically restricted is reduced. As can be shortened. Accordingly, the stress applied to the toner is reduced, toner deterioration is suppressed, and the developer can be used stably over a long period of time to form a good image.
In the present embodiment, the developing device in which the stirring charging member 30 also functions as a developer supply unit has been described. However, the present invention is not limited to this, and the stirring charging member 30 and the developer supply are not limited thereto. It is also possible to provide the developer regulating member 34a so as to be adjacent to the developer supply means. Even in this case, the time or distance from the time when the developer adheres to the developing sleeve 23 until the developer more than the necessary amount is peeled off is shortened, and the toner is prevented from being charged as much as possible. Can be suppressed.

In this embodiment, as a material of the magnet roll 22 forming the developing sleeve, for example, magnetic powder of Sr ferrite or Ba ferrite, PA (polyamide) material such as 6PA or 12PA, EEA (ethylene-ethyl copolymer) or It is preferable to use a plastic magnet or a rubber magnet in which an ethylene compound such as EVA (ethylene / vinyl copolymer), a chlorine material such as CPE (chlorinated polyethylene), and a polymer compound of a rubber material such as NBR are mixed. Further, the magnet molded body is a rod-like block extending in the developing roller axial direction, and it is desirable to use a material of Br> 0.5T (Tesla) in order to obtain a narrow and high magnetic property. For example, Ne-based (Ne / Fe / B, etc.) or Sm-based (Sm / Co, Sm / Fe / N, etc.) rare earth magnets or plastic magnets or rubber magnets obtained by mixing these magnet powders with the same polymer compounds as described above. Is used.

In this embodiment, as the toner, for example, a toner in which an additive is contained in particles is used. A conventionally well-known thing can be used as an additive. Specifically, oxides such as Si, Ti, Al, Mg, Ca, Sr, Ba, In, Ga, Ni, Mn, W, Fe, Co, Zn, Cr, Mo, Cu, Ag, V, and Zr And complex oxides. In particular, silica, titania, alumina and the like, which are oxides of Si, Ti, and Al, are suitable. The addition amount of the additive is preferably 0.5 to 1.8 parts by weight, particularly preferably 0.7 to 1.5 parts by weight with respect to 100 parts by weight of the base particles. When the amount of the additive is less than 0.5 parts by weight, the fluidity of the toner is lowered, so that sufficient chargeability cannot be obtained, which easily causes background staining and toner scattering. If the amount of the additive is more than 1.8 parts by weight, the fluidity is improved, but the cleaning of the photosensitive member due to chatter, blade turning, etc., or the filming on the photosensitive member by the additive released from the toner is performed. Is likely to occur. In addition, the durability of the cleaning blade, the photoconductor and the like is lowered, and the fixing property is deteriorated. Furthermore, toner dust is likely to occur in the fine line portion, and in particular, in the case of fine line output in a full-color image, dust is particularly generated due to an increase in the amount of adhesion because it is necessary to overlap toner of at least two colors. The trend becomes prominent. In the case of a color toner, if a large amount of additive is contained, the projected image is distorted when the toner image formed on the transparent sheet is projected by an overhead projector, and it is difficult to obtain a clear projected image. May be. Various methods for measuring the content of the additive are known, but fluorescent X-ray analysis is generally employed. The fluorescent X-ray analysis method is a method in which a calibration curve is prepared by a fluorescent X-ray analysis method for a toner having a known additive content, and the additive content is obtained using the calibration curve.

As a method for evaluating the deterioration of the toner over time, there is a method of observing peeling or embedding of the external additive. For example, it can be evaluated by observing the surface of the toner with an electron microscope. Specifically, about 0.1 g of toner is sampled from the developing unit and fixed to a sample stage of an electron microscope using a conductive carbon tape. Thereafter, the magnification can be evaluated by setting the observation magnification from 10,000 times to 50,000 times, sampling and observing about 30 toners, and ranking from the attached state of the external additives.
In the present embodiment, it is desirable to use toner that has been surface-treated with a treating agent. As the treating agent, organic silane compounds, for example, alkylchlorosilanes such as methyltrichlorosilane, octyltrichlorosilane, and dimethyldichlorosilane, and alkylmethoxysilanes such as dimethyldimethoxysilane and octyltrimethoxysilane are suitably used. Moreover, hexamethyldisilazane, silicon oil, etc. can also be used. Examples of the surface treatment method include a method of dipping a toner in a solution containing an organosilane compound and drying, a method of spraying and drying a solution containing an organosilane compound on the toner, and the like. The volume average particle diameter of the toner is preferably in the range of 3 to 7 μm, for example.

As the magnetic carrier, conventionally known ones such as iron powder, ferrite powder, magnetite powder, magnetic resin carrier having a particle diameter of about 20 to 200 μm can be used. In the present embodiment, a core having a mean particle size of 55 μm, for example, containing a magnetic material such as ferrite in a core made of metal or resin and having a surface layer coated with a silicone resin or the like is suitably used. As the coating material for the surface layer, amino resins such as urea-formaldehyde resin, melamine resin, benzoguanamine resin, urea resin, polyamide resin, epoxy resin and the like can be used. Further, polyvinyl resin, polyvinylidene resin, acrylic resin, polymethyl methacrylate resin, polyacrylonitrile resin, polyvinyl acetate resin, polyvinyl alcohol resin, polyvinyl butyral resin, polystyrene resin, or the like can also be used. Further, polystyrene resins such as styrene acrylic copolymer resins, halogenated olefin resins such as polyvinyl chloride, polyester resins such as polyethylene terephthalate resin and polybutylene terephthalate resin, and the like may be used. Further, polycarbonate resins, polyethylene resins, polyvinyl fluoride resins, polyvinylidene fluoride resins, polytrifluoroethylene resins, polyhexafluoropropylene resins, copolymers of vinylidene fluoride and acrylic monomers, and the like may be used. Furthermore, a copolymer of vinylidene fluoride and vinyl fluoride, a fluoroterpolymer such as a terpolymer of tetrafluoroethylene, vinylidene fluoride, and a non-fluorinated monomer, or a silicone resin may be used. In addition, you may contain electrically conductive powder etc. in coating resin as needed. As the conductive powder, metal powder, carbon black, titanium oxide, tin oxide, zinc oxide, or the like can be used. The average particle diameter of the conductive powder is preferably 1 μm or less. This is because when the average particle diameter is larger than 1 μm, it is difficult to control electric resistance.

Next, a modified example of the developing device according to the embodiment of the present invention will be described.
FIG. 3 is a diagram illustrating a modified example of the developing device. In FIG. 3, this developing device is provided with a scraper 32 as a developer collecting means for scraping off toner remaining on the surface of the developing sleeve 23 on the downstream side of the portion of the developing sleeve 23 facing the developing area of the photosensitive member 2. In addition, a conveyance path 33 for circulating the toner written by the scraper 32 to the developer stirring container 34 is provided.
After the developer charged by the stirring charging member 30 is supplied to the developing sleeve 23, the thickness thereof is regulated by one end 34a of the developer stirring container 34, and then supplied to the developing region on the surface of the photoreceptor 2. Develop the electrostatic latent image.
After the development, the developer remaining on the surface of the developing sleeve 23 is mechanically scraped off and collected by a scraper 32 positioned downstream in the rotational direction from the position facing the photoreceptor 2. The collected developer is conveyed to the developer stirring container 34 via the conveyance path 33 by a powder pump unit called a mono pump having a well-known structure using a conveyance screw and an airflow, for example.

According to the present embodiment, as in the above-described embodiment, since the time from when the toner is charged until it is regulated to the required amount can be shortened, the overall stress applied to the toner is reduced, and the toner is deteriorated. And a developer can be used stably over a long period of time to form a good image.
In the present embodiment, it is preferable to provide a toner supply device for replenishing the toner reduced by the development in the conveyance path 33. As a result, the stirring time after replenishing the toner can be increased as compared with the apparatus shown in FIG. 2, so that the stirring efficiency is improved and the toner concentration can be made more uniform.

In the present embodiment, the inner diameter of the inlet and outlet portions of the transport path 33 is made larger than the inner diameter of other portions, in other words, the cross-sectional area other than the inlet and outlet of the transport path 33 is larger than the cross-sectional area of the inlet and outlet. It is preferable to reduce the size. FIG. 4 is a schematic diagram illustrating an entrance portion of the conveyance path 33. In FIG. 4, a scraper 32 is provided adjacent to the developing sleeve 23, and the cross section other than the inlet of the transport path 33 for transporting the developer collected by the scraper 32 is smaller than the cross section of the inlet portion. Yes. As a result, the collected developer is, for example, once collected in the central portion and transported in the centralized state. In the middle of the transport, the toner is replenished, and again at the enlarged diameter portion of the exit portion of the transport path 33. Will be distributed. Therefore, the developer can be easily stirred and dispersed uniformly, and the density unevenness of the developer due to toner replenishment can be reduced. Further, the developer can be well dispersed and supplied to every corner of the developer stirring container 34 without any unevenness.

FIG. 5 is a diagram showing another modification of the developing device according to the present embodiment.
5, this apparatus differs from the apparatus shown in FIG. 3 in that a static eliminating device 35 for eliminating the developer remaining on the surface of the developing sleeve 23 is provided on the upstream side of the scraper 32 in the rotation direction of the photosensitive member.
According to the present embodiment, since the static eliminator 35 is arranged on the upstream side of the scraper 32, the developer remaining on the surface of the developing sleeve 23 can be collected after being neutralized in advance by the static eliminator 35. FIG. In addition to the effects of the apparatus, it is possible to suppress the deterioration of the developer due to the electrostatic adhesion force in the conveyance path. That is, according to the present embodiment, since the developer does not have an electric charge until the developer is collected and then transported to the developer stirring container 34, the developer is deteriorated due to electrostatic adhesion. Can be prevented. Further, since the new toner can be replenished in a state where the restraint due to the electrostatic adhesion force between the toner and the carrier is released, the toner density can be made uniform at a higher level.

In the present embodiment, for example, a corona charger or a roller-shaped member can be used as the static elimination device 35, and a DC + AC via is applied to the static elimination device 35, for example. The AC voltage to be applied to the static eliminator 35 is set to exceed the discharge start voltage determined by Paschen's law. For example, the amplitude voltage can be set to 1 kV to 20 kV and the frequency can be set to 100 Hz to 10 kHz. .

FIG. 6 is a diagram showing another modification of the developing device according to the present embodiment.
In FIG. 6, the image forming apparatus is configured such that a developer charging member 21 a and a developer amount regulating member 24 are arranged close to each other.
A DC or DC + AC bias is applied to the developing sleeve 23 from a developer carrier bias power supply (not shown). In this apparatus example, the developer introduced through a hopper (not shown) is supplied onto the developing sleeve 23 by the developer conveying member 21a. The developer supplied onto the developing sleeve 23 is conveyed in the rotation direction of the developing sleeve. The developer is transported to the position of the regulating member 24 and passes through the regulating member 24 to form a developer thin layer in an amount necessary for image output. Thereafter, the developer is transported to a developing area which is a portion facing the photoreceptor 2 and is supplied onto the photoreceptor 2 due to a bias difference between the photoreceptor 2 and the developing sleeve 23 to develop the electrostatic latent image. .
According to the present embodiment, the developer is statically moved by being close to each other so that the distance from the charged portion of the developer to the developer amount regulating member which is the last mechanism that stresses the developer is shortened. It is possible to reduce the stress due to the electric adhesion force, thereby preventing the deterioration of the developer.
In the conventional developing device, the developer supplied onto the developing sleeve is rubbed due to the magnetic force distribution of the magnet roller while being transported to the layer regulating member, and this rubbing causes the developer to move. Although this embodiment has a disadvantage that the deterioration proceeds, in the present embodiment, since the regulating member 24 is provided in the vicinity of the stirring charging member 23a, the regulating member 24 uses the regulating member 24 after the developer is supplied to the developing sleeve 23. The time until the amount is regulated is shortened, thereby reducing the stress and deterioration of the developer and achieving a long life.
Although the present invention has been described in detail with reference to examples, the present invention is not limited to these.

In the above embodiments, the case where the developing device according to the present invention is applied to a developing device that forms a single color image has been described. However, the developing device of the present invention is also suitable for an image forming device that forms a color image. Applied.
FIG. 7 is an explanatory view showing an example in which the developing device of the present invention is applied to an image forming apparatus for forming a color image. FIG. 7A is a schematic configuration diagram of a tandem type full-color image forming apparatus, and FIG. FIG. 2B is a schematic configuration diagram of a revolver type full-color image forming apparatus.
In FIG. 7A, the image forming apparatus 1 is a tandem type full-color image forming apparatus and corresponds to, for example, each color of cyan (C), magenta (M), yellow (Y), and black (K). The image forming units are arranged horizontally on the same plane. Each image forming unit mainly includes a photosensitive member 2 that is driven to rotate clockwise in the drawing, and a charging device 3, a writing device 4, and a developing device 5 that are arranged around the photosensitive member 2. An intermediate transfer belt 7 indicated by a pair of support rollers is provided below the image forming unit row, and a paper transfer roller via the intermediate transfer belt 7 with respect to one support roller that supports the intermediate transfer belt 7. 6 is provided. In addition, this apparatus is accommodated in the housing | casing which was not illustrated, for example. As the developing device 5, any one of the developing devices described above is applied.
The image forming apparatus 1 includes a paper feed cassette that stores a plurality of recording papers (not shown). The paper feeding cassette feeds recording papers one by one by a paper feeding roller, and a pair of registration rollers (not shown). After the timing is adjusted, the sheet is fed between the transfer roller 6 and the intermediate transfer belt 7.
In the image forming apparatus 1 having such a configuration, in each image forming unit, the photosensitive member 2 is rotationally driven, for example, clockwise in the figure, and the surface of the photosensitive member 2 is uniformly charged by the charging device 3, and then the writing device. An electrostatic latent image is formed on the photosensitive member 2 by irradiating laser light modulated by image data 4. The developing device 5 attaches toner to the photoreceptor 2 on which the electrostatic latent image is formed, and develops the electrostatic latent image. Thereafter, toner images corresponding to the respective colors formed on the respective photoreceptors 2 are sequentially transferred and laminated on the intermediate transfer belt 7 to form a color image. Next, the color image is transferred to the recording paper P supplied to the contact portion between the intermediate transfer belt 7 and the transfer roller 6. The recording paper on which the color image has been transferred is introduced into a fixing device (not shown) and fixed.

FIG. 7B is a diagram illustrating a schematic configuration of a revolver type full-color image forming apparatus. In this image forming apparatus, a plurality of color toners are successively developed on one image carrier by switching the operation of the developing device. That is, in FIG. 7B, the charging device 3, the exposure device 4, and the cleaning device 13 are arranged around the photoconductor 2 as an image carrier. An image forming unit corresponding to, for example, each of cyan (C), magenta (M), yellow (Y), and black (K) is disposed on the downstream side in the rotation direction of the photosensitive member 2 so as to be adjacent to the exposure device 4. 5 are sequentially arranged. On the downstream side of the image forming unit 5, an intermediate transfer belt 7 that is supported by a support roller so as to contact the photoreceptor 2 is provided. A transfer roller 6 is provided so as to come into contact with one support roller that supports the intermediate transfer belt 7 via the intermediate transfer belt 7. As the developing device 5, any one of the above-described developing devices is applied.
In such a configuration, a single color toner image corresponding to each color formed on the surface of the photoreceptor 2 by each developing device 5 (C, M, Y, K) is sequentially transferred onto the intermediate transfer belt 7 and laminated. To form a color image. Next, the color image formed on the transfer belt 7 is transferred to the recording paper p separately supplied to the contact portion between the transfer roller 6 and the intermediate transfer belt 7. Next, the recording paper P to which the color image has been transferred is conveyed to a fixing device (not shown) and the transferred image is fixed on the recording paper P to obtain a fixed image.
On the other hand, the photosensitive member 2 on which the color toner image is transferred to the recording paper P is further rotated, and the toner remaining on the surface of the photosensitive member 2 is scraped off by, for example, a blade and collected by the cleaning device 13. Next, the surface of the photoreceptor 2 from which the residual toner has been removed is neutralized by the neutralization device 8. The surface of the photoreceptor 2 that has been neutralized is uniformly charged by the charging device 3, and then the same operations as described above are sequentially repeated to continuously form an image. The cleaning unit 13 is not limited to the one that scrapes the residual toner on the photoconductor 2 with a blade, and may be one that scrapes the residual toner on the photoconductor 2 with a fur brush, for example.

In this embodiment, similarly to the above-described embodiment, the stirring charging member 30 also functions as a developer supply device, and the developer regulating member 34a substituted by one end of the casing 34 so as to be adjacent to the stirring charging member 30. (See FIG. 2), the time from when the toner starts to be charged until it is regulated to the required amount can be shortened, and the time when the toner is unnecessarily charged is reduced. Since the toner is shortened, stress applied to the toner is reduced, deterioration is suppressed, and the developer can be used stably over a long period of time to form a good image.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a diagram illustrating a schematic configuration of a developing device according to an embodiment of the present invention. It is a figure which shows the modification of the developing device which concerns on embodiment of this invention. It is a figure which shows the entrance part of the conveyance path of the developing device which concerns on embodiment of this invention. It is a figure which shows another modification of the developing device which concerns on embodiment of this invention. It is a figure which shows another modification of the developing device which concerns on embodiment of this invention. It is a figure which shows schematic structure of another image forming apparatus which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Photoconductor 3 Charging apparatus 4 Writing apparatus 5 Developing apparatus 6 Transfer apparatus (transfer roller)
7 Intermediate transfer body 8 Static elimination device 13 Cleaning device 13a Blade 22 Magnet roller 23 Development sleeve 24 Restriction member 30 Developer stirring member 31 Hopper 32 Scraper 33 Transport path 34 Developer stirring container 34a Developer regulation member 35 Static elimination device

Claims (5)

A developer carrier for developing the electrostatic latent image by supplying a developer to the image carrier;
Developer supplying means for supplying a developer to the developer carrying member to form a developer thin film on the surface thereof;
Developer regulating means for regulating the thickness of the thin film developer;
Agitation charging means for agitating and charging the developer supplied to the developer carrying member in advance;
In a developing device having
It said agitating charging means which functions also as the developer supply means, the stirring charging means and said developer regulating means is provided, et al is in a rotational direction downstream side of the developer carrying member adjacent the,
Developer collecting means for collecting the developer remaining on the developer carrying member at a position facing the downstream side surface in the rotational direction from the portion of the developer carrying member facing the developing region of the image carrier. A transport path for returning the developed developer to the developer agitating container, and toner supply means for replenishing toner in the transport path is provided,
A developing device, characterized in that a discharging means for discharging the developer collected by the developer collecting means is provided on the upstream side of the developer carrying member in the rotation direction of the developer carrying member . The developing device according to claim 1, wherein the developer regulating unit is a casing of a developer stirring container that houses the stirring charging unit. 3. The developing device according to claim 1 , wherein a cross-sectional area of a portion other than the inlet and the outlet of the transport path is smaller than a cross-sectional area of the inlet and the outlet . In a process cartridge in which an image carrier and a developing device that develops an electrostatic latent image formed on the surface of the image carrier are integrated and detachably formed on the image forming apparatus main body,
The developing device according to claim 1, wherein the developing device is a developing device according to claim 1.
A process cartridge characterized by that. An image carrier;
A charging device for uniformly charging the surface of the image carrier;
An exposure device that forms an electrostatic latent image on the charged image carrier surface based on image information;
A developing device for supplying a developer to the electrostatic latent image to visualize the electrostatic latent image;
A transfer device for transferring a visible image formed on the surface of the image carrier to a recording medium directly or via an intermediate transfer member;
In an image forming apparatus having
The developing device is the developing device according to any one of claims 1 to 3 or the developing device for a process cartridge according to claim 4.
An image forming apparatus.

Images