JP2009069670A - Developing device, process cartridge, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device in which toner is supplied to a toner carrier for development, while separating the toner from the surface of a toner carrier by the electric field between electrodes and forming a cloud. <P>SOLUTION: The developing device 13 has: a first toner carrier 13A having a plurality of electrodes inside and an electric field generating member having a voltage supplying means supplying a voltage to the electrodes, so as to temporally change the electric field between the plurality of electrodes, so that the toner is separated from the surface by the electric field between the electrodes and the cloud is formed; a toner supplying means 13h for supplying the toner to the electric field generating member surface of the first toner carrier 13A; a toner regulating member 13c regulating the toner layer of the electric field generating member surface of the first toner carrier 13A; a toner storage section 13g for storing the toner; and a toner stirring member 13d stirring the toner of the toner storage section 13g. A second toner carrier 13B developing the electrostatic latent image of an image carrier 11 is provided near the first toner carrier 13A. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a developing device, a process cartridge provided with the developing device, and an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine including the developing device or the process cartridge.

2. Description of the Related Art Conventionally, developing devices used in image forming apparatuses such as copying machines, printers, and facsimiles include a two-component developing method and a one-component developing method.
Of these, the two-component development method is very suitable for high-speed development, and is the mainstream method of current medium-speed and high-speed image forming apparatuses.

  The one-component developing method is currently the mainstream method for low-speed image forming apparatuses because the mechanism is small and light. In this one-component development system, in order to form a toner thin layer on the developing roller, a toner regulating member such as a blade or a roller is brought into contact with the toner on the developing roller. The toner is charged by the friction. The charged toner layer formed in a thin layer on the developing roller is conveyed to a developing unit facing the image carrier such as a photoconductor to develop the electrostatic latent image on the image carrier.

The developing system is roughly divided into a contact type and a non-contact type. The former is a type in which the developing roller and the image carrier are in contact, and the latter is a type in which the developing roller and the image carrier are not in contact. is there.

  By the way, in the image-on-image forming process in which the first toner image is formed on the image carrier and the second toner image and the third toner image are sequentially formed thereon, In addition, it must be a non-contact developing system that does not disturb the toner image formed on the image carrier.

  In the above two-component development method, since a magnetic spike is formed in the developing portion, it is difficult to form a stable gap between the developing roller and the image carrier. In addition, the developer layer is thicker than that of a one-component developing device, and a phenomenon called a so-called edge effect is likely to occur and is not suitable for a non-contact type. On the other hand, in the one-component development method, since the toner layer on the developing roller is thinned, it can be developed in a non-contact manner by forming an alternating electric field. However, since the toner layer is stressed to make the toner layer thinner, it is difficult to achieve high durability.

  In order to compensate for the disadvantages of the two-component development method and the one-component development method, the conventional techniques described in Patent Document 1 (Japanese Patent Laid-Open No. 3-110355) and Patent Document 2 (Japanese Patent Laid-Open No. 2002-182467) are used. In addition, as a developing device that can supply and carry toner charged to a predetermined polarity on a developing roller without using frictional charging by a contact member on a developing roller, a magnetic brush made of a two-component developer is provided on the surface. There has been proposed a hybrid developing device that uses a formed toner supply member and hybridizes a two-component developing method and a one-component developing method in which only toner is supplied from a magnetic brush on the toner supplying member to a toner carrier. Yes. In these developing devices, a two-component developer is carried on a toner supply member (magnetic roller, magnetic brush forming body) to form a magnetic brush. The toner in the magnetic brush is charged to a predetermined polarity by friction with the magnetic particles. Only the toner charged to a predetermined polarity from the magnetic brush on the toner supply member is moved and carried on the toner carrier (developing roller, toner layer holder).

  As a non-contact type development method, for example, there is a method as in the prior art described in Patent Document 3 (Japanese Patent Laid-Open No. 3-113474). In this method, a high-resolution dot developability is realized by installing a wire to which a high-frequency bias is applied to the developing unit, to form a toner cloud in the developing unit, as compared to the hybrid method.

Japanese Patent Laid-Open No. 3-100575 JP 2002-182467 A JP-A-3-113474

  In the two-component development method, the demand for higher image quality is increasing, and the required dot size of the pixel itself is required to be equal to or smaller than the current carrier particle diameter. In this sense, it is necessary to further reduce the carrier particles. However, as the carrier diameter is reduced, the permeability of the carrier particles decreases, so that the carrier tends to be detached from the developing roller. If the detached carrier particles adhere to the image carrier, the carrier adheres. Not only does this cause image defects, but it also causes various side effects such as damaging the image carrier from that point.

  In order to prevent this carrier detachment, attempts have been made to increase the magnetic permeability of carrier particles from the material surface and to increase the magnetic force of the magnet included in the developing roller. Development is extremely difficult due to this balance. In addition, due to the downsizing of the developing roller, the developing roller is becoming smaller in diameter, and it becomes difficult to design a developing roller having a strong magnetic field configuration that can completely prevent carrier detachment. Yes.

  In the first place, the two-component development method is a process of forming a toner image by rubbing the ears of a two-component developer called a magnetic brush against the electrostatic latent image. Unevenness tends to occur in the developability. Although an image quality can be improved by forming an alternating electric field between the developing roller and the latent image carrier, it is difficult to completely eliminate the fundamental image unevenness such as the unevenness of the ears of the developer.

  In order to improve transfer efficiency and cleaning efficiency in the step of transferring the developed toner image on the image carrier and the step of cleaning the toner remaining on the image carrier after the transfer, It is necessary to reduce the non-electrostatic adhesion with the toner as much as possible. As a method for reducing the non-electrostatic adhesion between the image carrier and the toner, it is known that it is effective to reduce the coefficient of friction on the surface of the image carrier. Since the spikes pass through the developing portion smoothly, the developing efficiency and the dot reproducibility become very poor.

In the one-component development method, since magnetic particles are not used, a phenomenon that development unevenness occurs somewhat due to the influence of the state in which the magnetic brush of the two-component developer strikes the image carrier, which is not faithful to the electrostatic latent image. Magnetic brush mark does not occur. Furthermore, the developer layer is thinner than in a two-component developing device, and there is little phenomenon called the so-called edge effect. For this reason, the one-component developing device is excellent in reproducibility of high-definition images. Among them, the one using a non-magnetic one-component developer is excellent in colorization and suitable as a developing device for obtaining a high-definition color image.
However, in this one-component development method, a very large stress is applied to the toner when the toner thin layer is formed on the developing roller, so that the toner circulating in the developing device is deteriorated very quickly. As the toner deteriorates, unevenness and the like easily occur in the process of forming a toner thin layer on the developing roller, and the one-component developing method is generally not suitable as a high-speed and high-durability image forming apparatus.

In the above-described hybrid system of the two-component development system and the one-component development system, several problems are overcome. However, since the two-component developer is used, the carrier deteriorates due to the stirring of the toner and the carrier and the charging performance is lowered. Therefore, the carrier needs to be periodically replaced.
Further, although the method described in Patent Document 2 is considered to realize highly stable and high-quality development, the configuration of the developing device becomes complicated.

  To solve the above-mentioned problems of the prior art, in the toner supply method of the type “to form a cloud by separating the toner from the surface of the toner carrier by the electric field between the electrodes” according to the present invention described later, the toner particles are electrostatically conveyed. Since charging is performed while vibrating so as to jump off the surface of the member, a carrier for charging is not required unlike the two-component development method. In most of the time, the toner particles and the surface of the toner carrier are not in contact with each other. Accordingly, the electrostatic force between the toner particles and the surface of the toner carrier is weak. Therefore, compared to the conventional one-component development method, since the stress on the toner is less, high durability can be achieved.

  Further, in the normal one-component development method, the toner layer on the developing roller thinned by the toner regulating member is sufficiently pressed against the developing roller, so that the toner response to the electric field in the developing unit Sex is very bad. Therefore, in general, in order to obtain high image quality, it is the mainstream to form a strong alternating electric field between the developing roller and the image carrier, but even if this alternating electric field is formed, Therefore, it is difficult to stably develop a fixed amount of toner, and it is difficult to uniformly develop high resolution minute dots. However, in the toner supply method of the present invention, in which the toner is separated from the surface of the toner carrier by the electric field between the electrodes to form a cloud, the toner particles are developed while vibrating so as to jump off the surface of the electrostatic conveying member. Since the toner is supplied to the roller, the layer can be thinned without being pressed onto the developing roller, so that the toner responsiveness is increased and the image quality can be improved.

The present invention has been made in view of the above points. A developing device having a novel configuration for supplying toner to a developing toner carrier while forming a cloud by separating the toner from the surface of the toner carrier by an electric field between electrodes. The purpose is to provide.
Another object of the present invention is to provide a process cartridge and an image forming apparatus provided with the developing device having the novel configuration.

In order to achieve the above object, the present invention employs the following solutions.
According to a first aspect of the present invention, there is provided a developing device that develops an electrostatic latent image on an image carrier with a toner to make a visible image, the toner carrier having a plurality of electrodes therein, A voltage supply means for supplying a voltage to the electrodes so that the electric field between the electrodes changes with time, and an electric field generating member for separating the toner from the surface of the toner carrier by the electric field between the electrodes to form a cloud; A first toner carrier, toner supply means for supplying toner to the surface of the electric field generating member of the first toner carrier, and a toner layer on the surface of the electric field generating member of the first toner carrier. A toner regulating member for regulating, a toner storage unit for storing toner for use in development, and a toner agitating member for agitating the toner in the toner storage unit, in proximity to the first toner carrier. Before Characterized in that a second toner carrier to a developing unit for developing an electrostatic latent image on the image bearing member.

According to a second means of the present invention, in the developing device of the first means, the first toner carrier and the second toner carrier are not in contact with each other.
According to a third means of the present invention, in the developing device of the first or second means, a voltage supply means for supplying a voltage to the electrode of the first toner carrier, and a second toner carrier The voltage supply means for supplying the voltage is common.

According to a fourth means of the present invention, in the developing device of any one of the first to third means, the first toner carrier having the plurality of electrodes is stored inside the developing device casing. It is characterized by.
According to a fifth means of the present invention, in the developing device according to any one of the first to fourth means, the second toner carrier and the image carrier are not in contact with each other. .

According to a sixth means of the present invention, after the electrostatic latent image on the image carrier is developed with a toner to form a visible image, the toner image on the image carrier is finally transferred to a recording material to obtain an image. In the image forming apparatus for forming, the developing device of any one of the first to fifth means is provided as means for developing the electrostatic latent image on the image carrier.
A seventh means of the present invention is the image forming apparatus of the sixth means, comprising a plurality of the developing devices, wherein an image obtained by superimposing a plurality of toner images on the image carrier is recorded on the recording material. To form a multicolor or full-color image.

According to an eighth aspect of the present invention, there is provided a process cartridge provided in an image forming apparatus for forming an image by an electrophotographic process, comprising at least the developing device of any one of the first to fifth means. It is characterized in that it is detachable from the forming apparatus.
According to a ninth aspect of the present invention, there is provided an image forming apparatus for forming an image by an electrophotographic process, comprising a single or a plurality of process cartridges of the eighth means to form a single color, a multicolor or a full color image. It is characterized by.

  In the developing device of the first means, since the toner is vibrated and charged by the first toner carrier having the electric field generating member for forming the cloud, the toner on the second toner carrier is frictionally charged. Since there is no need to provide a contact member, there are no problems such as toner filming on the second toner carrier, and changes in development characteristics over time due to wear of the toner carrier and the contact member. Further, since a two-component developer is not used, it is not necessary to periodically replace a deteriorated carrier.

  In the developing device of the second means, the linear velocity ratio can be set to 2.5 times or more by making the first toner carrier and the second toner carrier non-contact with each other. The contact probability between the toner carrier and the toner on the second toner carrier can be increased. As a result, the toner supply capability is increased, and even when a large amount of toner on the toner carrying member is consumed in the development of the solid image, the toner carrying amount on the toner carrying member can be quickly recovered.

  In the developing device of the third means, voltage supply means for supplying voltage to the a-phase or b-phase electrode of the first toner carrier and voltage supply means for supplying voltage to the electrode of the second toner carrier are provided. By using the common toner, it is possible to efficiently supply the toner from the first toner carrier to the second toner carrier. Further, since the voltage supply means can be shared, miniaturization can be achieved.

  In the developing device of the fourth means, the first toner carrier having a plurality of electrodes that cloud the toner by an electric field is stored inside the developing device housing and sealed, thereby preventing the toner from scattering to the outside of the device by the cloud. Can be prevented. Further, since the first toner carrier can be shielded from the outside air, it is difficult to be affected by the temperature and humidity of the outside air, so that a stable cloud state can be maintained.

  In the developing device of the fifth means, by supplying the toner to the second toner carrier by the cloud, the toner layer can be thinned without pressing the toner, so that the second toner carrier, the image carrier, By forming an alternating electric field without contact, toner responsiveness is good and a certain amount of toner can be stably developed, so that high image quality can be achieved.

In the image forming apparatus of the sixth means, any one of the first to fifth means is provided by providing the developing device of any one of the first to fifth means as means for developing the latent image on the image carrier. Thus, the effect of one means can be obtained, and stable and good image formation can be performed.
In the image forming apparatus of the seventh means, in addition to the effect of the sixth means, an image obtained by superimposing a plurality of toner images on the image carrier is formed on the recording material, thereby stably Good multicolor or full color images can be formed.

  In the process cartridge of the eighth means, it is possible to provide a process cartridge capable of performing stable and good image formation by providing at least the developing device of any one of the first to fifth means. . Further, since the process cartridge is detachably attached to the image forming apparatus, the process cartridge can be easily replaced or recycled, which contributes to improvement of maintainability of the image forming apparatus and resource saving. it can.

  In the image forming apparatus of the ninth means, one or more process cartridges of the eighth means are provided, and a single color, multicolor or full color image is formed, thereby stably forming a good single color, multicolor or full color image. can do. Further, since the process cartridge is detachably attached to the main body of the image forming apparatus, it can be easily replaced or recycled, which contributes to improving the maintainability of the image forming apparatus and saving resources. it can. In addition, maintenance and management of the image forming apparatus are facilitated.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In each figure, the same part is represented by the same symbol.
FIG. 1 is a schematic configuration diagram showing one configuration example of an image forming apparatus to which the present invention can be applied. In the image forming apparatus 10 shown in FIG. 1, reference numeral 11 denotes an image carrier in which a negatively charged organic photoconductor (OPC) is configured in a belt shape. The image carrier 11 includes a plurality of rollers 11b including a driving roller and a driven roller. , 11c, 11d, and is provided so as to be rotated in the direction of the arrow in the figure by a rotary drive mechanism (not shown). In addition, the image carrier 11 includes a plurality of developing cartridges 13K, 13M, 13C, which have different colors (for example, black (K), magenta (M), cyan (C), and yellow (Y)) of toner used for development. 13Y and charging devices 12K, 12M, 12C, and 12Y, which will be described later, and writing devices 14K, 14M, 14C, and 14Y are arranged to face each color, and are charged and exposed as the image carrier 11 moves. Optical writing) and development electrophotographic processes are performed, and toner images of respective colors are sequentially stacked on the image carrier 11 (this is referred to as “one-pass color”).

  An image forming unit for each color including the developing cartridges 13K, 13M, 13C, and 13Y, the charging devices 12K, 12M, 12C, and 12Y, and the writing devices 14K, 14M, 14C, and 14Y is selected by control of a control unit (not shown). In accordance with information (for example, black and white, multicolor, full color, etc.) selected by an operation unit (not shown), a single color image forming unit (for example, black developing cartridge 13K, charging device) can be driven. 12K, writing device 14K) is driven to form a single color image (monochrome image) on the image carrier, and driving two or three color image forming units drives a multicolor image on the image carrier. When all the image forming units are driven, a full color image is formed on the image carrier.

  In the image forming apparatus 10 of FIG. 1, reference numeral 15 denotes a paper feeding device that stores a transfer material such as recording paper and starts conveying the transfer material at the time of image formation, and includes a paper feeding cassette, a paper feeding roller, and a separation roller. Etc. Reference numeral 16 denotes a transfer roller for transferring an image formed on the image carrier 11 to a transfer material, and reference numeral 17 denotes a fixing device for fixing the unfixed toner image formed on the transfer material by heating and pressing. Reference numeral 18 denotes a paper discharge tray for discharging the transfer material after fixing. Reference numeral 19 denotes a cleaning device that cleans the surface of the image carrier after transferring the toner image to remove residual toner, paper dust, and the like. In the image forming apparatus of FIG. 1, the cleaning device 19 for collecting the transfer residual toner particles on the surface of the image carrier 11 is provided. However, the cleaning device 19 may not be provided. When the cleaning device 19 is not provided, the transfer residual toner particles remain on the surface of the image carrier 11, but are charged by the four charging devices 12 and eventually transferred to the transfer material and removed from the image carrier 11. The When the transfer residual toner particles are transferred to the transfer material, some image disturbance occurs, but if the transfer residual toner particles are slightly disturbed, they are not visually recognized.

  In the image forming apparatus 10 of FIG. 1, at the time of image formation, a toner image of each color is superimposed on the image carrier 11 by the above-described electrophotographic process to form a full color image (or a single color image or a multicolor image). The transfer material sent from the paper feeding device 15 in synchronization with the formation is conveyed to the contact portion between the image carrier 11 and the transfer roller 16, and the image formed on the image carrier 11 is transferred at the contact portion. Transfer is performed on the transfer material by the voltage applied to the roller 16. Thereafter, when the transfer material reaches the fixing device 17, the toner image on the transfer material is fixed on the transfer material by being heated and pressed while being sandwiched between the heating roller 17a and the pressure roller 17b, and then on the transfer material. A visible image is formed. Then, the transfer material after fixing is discharged to the paper discharge tray 18.

  The developing cartridges 13K, 13M, 13C, and 13Y used in the image forming apparatus 10 having the above-described configuration develop black (K), magenta (M), cyan (C), and yellow (Y) toner images, respectively. Development cartridge. The developing cartridges 13K, 13M, 13C, and 13Y are detachable from the open space by the image carrier 11 rotating and retracting downward with the roller 11c as a fulcrum as shown in FIG. Can be easily exchanged.

  The writing devices 14K, 14M, 14C and 14Y expose the charged image carrier 11 with the light beams LK, LM, LC and LY according to the image information, and black (K), magenta (M) and cyan (C), respectively. ), A device for writing a latent image corresponding to yellow (Y) color, an optical scanning device using a laser light source, an optical deflector (polygon scanner, vibrating mirror, etc.) and a scanning imaging optical system, and an LED array Various devices such as a line-type writing device using a lens array can be used.

  Next, means for forming a toner image on the image carrier, such as the developing cartridge of this example, will be described with reference to FIG. Since the developing cartridges of the respective colors have the same structure, only one will be described as an example.

  In FIG. 2, reference numeral 12 (12K, 12M, 12C, 12Y in FIG. 1) denotes a charging device for uniformly charging the surface of the image carrier 11, and in this embodiment, corona charging is adopted. If non-contact charging means such as corona charging is used, the image carrier 11 can be charged without disturbing the toner image formed by the upstream developing cartridge.

Reference numeral 13 (13K, 13M, 13C, 13Y in FIG. 1) denotes a developing cartridge = developing device, and the toner carrier 13a is 50 to 1000 μm, preferably 150 to 400 μm, with respect to the image carrier 11 during image formation. Opposite non-contact with a gap.
2 is provided with a supply roller 13h for supplying toner particles to the toner carrier 13a. The toner carrier 13a and the supply roller 13h are rotated by a rotation drive mechanism (not shown). It has become so.

  A toner regulating member 13c that regulates the toner layer is formed in the upstream portion of the developing region in the toner transport direction to form a toner thin layer. The regulating member 13c is brought into contact with the toner by a blade or a roller, and at that time, the toner is charged by friction between the toner carrying member 13a or the toner regulating member 13c and the toner. Further, a paddle 13d, which is a toner stirring member for pumping the toner in the developing casing 13e to the supply roller 13h while stirring the toner in the developing roller 13e, is installed in a region opposite to the image carrier 11 of the supply roller 13h.

The toner storage unit in the developing casing 13e of the developing device 13 stores toner particles (not shown). Hereinafter, the aspect of the toner in this embodiment will be described.
The toner particles of this example may be obtained by radical polymerization in the state where a styrene or acrylic polymerizable monomer is dispersed in water together with a polymerization initiator as a binder resin, or a polyester resin is dispersed in water. Non-magnetic toner particles having a weight average particle diameter of about 5 μm obtained by granulating using a polymer obtained by addition reaction and adding a colorant, a charge control agent and the like to this.

Next, an operation for forming a toner image on the image carrier will be described.
First, the surface of the image carrier 11 is uniformly charged by the charging device 12. Even when a toner image has already been formed on the image carrier 11, the surface of the image carrier 11 including the toner image is uniformly charged. Next, a light beam L corresponding to the image information is irradiated from a writing device (14K, 14M, 14C, 14Y in FIG. 1) (not shown). Since the light beam L passes between the charging device 12 and the developing cartridge 13, the light beam L is applied to the image carrier 11 that has already been uniformly charged, and is a negatively chargeable photoconductor. On the surface of the image carrier 11, a region corresponding to the image portion is neutralized to form a latent image.

  The developing cartridge 13 attaches toner particles to the image portion of the latent image formed on the image carrier 11 and visualizes the latent image as a toner image. The above-described charging, light beam irradiation, and development steps are repeated at the facing portions of the developing cartridges (13K, 13M, 13C, and 13Y in FIG. 1) as described above, and four color toner images are formed on the image carrier 11. A full-color image in which is superimposed is formed.

  In the image forming apparatus 10 of FIG. 1, in a normal image forming operation, a transfer material such as a recording sheet supplied from a paper feed cassette of the paper feed device 15 by a paper feed roller or the like is transported by a transport roller or a transport belt (not shown). It is conveyed toward the top of the apparatus and sent to a transfer unit where the image carrier 11 and the transfer roller 16 abut. The transfer material moves while being sandwiched between the transfer roller 16 and the image carrier 11, and the toner image is transferred from the image carrier 11 during the movement. When the transfer material passes through the transfer portion, is conveyed by a conveyance roller or a conveyance belt (not shown), and reaches the fixing device 17, the toner image on the transfer material is heated while being sandwiched between the heating roller 17a and the pressure roller 17b. Thus, the toner image is fixed on the transfer material, and a visible image is formed on the transfer material.

  In the mode for adjusting the color misregistration and toner density of each color toner image, the developing cartridges 13K, 13M, 13C, 13Y, the charging devices 12K, 12M, 12C, 12Y, the writing devices 14K, 14M, 14C, 14Y. A toner image for each color of a predetermined pattern is formed on the image carrier 11 by the image forming unit for each color, and the toner pattern is detected by an optical sensor (P sensor) (not shown), and based on the detection result The writing timing of each color writing device, the change of the developing bias, and the like are performed, so that an optimum color image can be obtained. Further, the toner pattern on the image carrier 11 is adjusted for the polarity of the charge by the bias applied to the transfer roller 16, and then the color of each color is determined by the voltage applied to the developing opposing rollers 11aK, 11aM, 11aC, and 11aY for each color. Collected in the developing cartridge.

The transfer roller 16 facing the image carrier 11 has at least a cored bar and a conductive elastic layer covering the cored bar. The conductive elastic layer is an elastic material such as polyurethane rubber, ethylene-propylene-diene polyethylene (EPDM), or the like. A transfer material that is an elastic body in which a conductivity imparting agent such as carbon black, zinc oxide, tin oxide or the like is mixed and dispersed in the material to adjust the electric resistance (volume resistivity) to a medium resistance of 10 ⁶ to 10 ¹⁰ Ω · cm. Laura.

  The image forming apparatus according to an embodiment to which the present invention is applied has been described above. In the developing device having the configuration shown in FIG. 2, the toner on the toner carrier 13a thinned by the toner regulating member 13c is used. Since the layer is sufficiently pressed on the toner carrier 13a, the toner responsiveness to the electric field at the developing portion is very poor. Therefore, usually, in order to obtain high image quality, it is mainstream to form a strong alternating electric field between the toner carrier 13a and the image carrier 11, but even if this alternating electric field is formed, the electrostatic latent It is difficult to stably develop a certain amount of toner on an image, and it is difficult to uniformly develop high resolution minute dots.

  Therefore, the developing device according to the present invention employs a toner supply method of the type “to form a cloud by separating the toner from the surface of the toner carrier by the electric field between the electrodes”, and the first toner carrier by the electric field between the electrodes. As a configuration for supplying toner to the second toner carrier for development while being separated from the surface and forming a cloud, the toner can be thinned without being pressed onto the second toner carrier. As a result, the toner can be thinned without being pressed onto the second toner carrier for development, so that the toner responsiveness is increased and the image quality can be improved. Hereinafter, specific examples of the present invention will be described.

[Example 1]
An embodiment of the first means will be described with reference to FIG.
The developing device 13 shown in FIG. 3 is a toner carrier having a plurality of electrodes therein, and a voltage supply means (not shown) for supplying a voltage to the electrodes so that the electric field between the electrodes changes with time. The first toner carrier 13A having an electric field generating member that separates the toner from the surface of the toner carrier by the electric field between the electrodes and forms a cloud, and the toner on the surface of the first toner carrier 13A. Toner supply means 13h for supplying the toner, a toner regulating member 13c for regulating the toner layer on the surface of the electric field generating member of the first toner carrier 13A, and a toner storage section for storing the toner used for development 13g and a toner agitating member 13d for agitating the toner in the toner storage portion 13g, in the vicinity of the first toner carrier 13A, a developing unit for developing the electrostatic latent image on the image carrier 11 Is obtained by a structure in which a second toner carrying member 13B.

More specifically, a first toner carrier 13A having a plurality of electrodes therein is installed in the developing casing 13e of the developing device 13, and on the left side of the first toner carrier 13A, A toner supply roller 13h, which is a toner supply means for supplying toner particles to the first toner carrier 13A, is disposed. The toner carrier 13A and the toner supply roller 13h are rotated by a rotation drive mechanism (not shown). It has become so.
In addition, a toner regulating member 13c that regulates the toner layer is formed on the downstream side of the toner supply roller 13h in the toner transport direction of the first toner carrier 13A to form a toner thin layer. The toner regulating member 13c is brought into contact with the toner with a blade, a roller, or the like, and regulates the toner to a certain amount.

Here, the configuration of the electric field generating member of the first toner carrier 13A will be described in detail with reference to FIG.
FIG. 4 is an enlarged partial sectional view of the image carrier 11 side surface of the electric field generating member of the first toner carrier 13A. The electric field generating member of the first toner carrier 13A moves the plurality of electrodes 102-1a, 102-1b, 102-2a, 102-2b,... 102-na, 102-nb onto the support base 101. The insulating transport surface forming member that forms the transport surface is formed on the electrode 102 at a required interval along the direction, and is formed of an inorganic or organic insulating material that is a protective film that covers the surface of the electrode 102. A surface protective layer 103 is laminated.

As the supporting base material 101 in the present embodiment, a base material made of an insulating material such as a glass base material, a resin base material, or a ceramic base material, or a substrate made of a conductive material such as stainless steel (SUS) is made of SiO _2. For example, a base material made of a material that can be deformed flexibly such as a polyimide film or the like can be used.

  The electrode 102 is formed by depositing a conductive material such as Al or Ni—Cr on the support base 101 with a thickness of 0.1 to 10 μm, preferably 0.5 to 2.0 μm, and using a photolithographic technique or the like. It is used by patterning into the required electrode shape. The width R of the plurality of electrodes 102 is 1 to 20 times the average particle diameter of the powder (toner particles).

As the surface protective layer 103, for example, SiO ₂ , TiO ₂ , TiO ₄ , SiON, BN, TiN, Ta ₂ O _{5 and the} like are formed to a thickness of 0.5 to 10 μm, preferably 0.5 to 3 μm. Formed.

  FIG. 5 shows the appearance of the first toner carrier 13A, which has two-phase electrodes (a-phase electrodes 1a, 2a..., B-phase electrodes 1b, 2b...), And a-phase electrodes. The axis A and the b-phase electrode axis B can be rotated as rotation axes. A bias potential can be applied to each electrode shaft by an electrode brush (not shown).

FIG. 6A shows an example of a cross-sectional configuration of the first toner carrier 13A. As shown in FIG. 6A, a shaft hole is provided in the cylinder of the support base 101, and the conductive toner is made of conductive metal. The electrode shaft A and the electrode shaft B are press-fitted.
FIG. 6B is a view of the first toner carrier 13A viewed from a direction parallel to the axis. In FIG. 6B, the a-phase electrode extends from the left electrode axis A to the b-phase electrode. The electrode protrudes from the right electrode axis B and has a comb-like electrode configuration with a phase and b phase. The end of the first toner carrier 13A is a solid electrode, which is wired through an electrode brush or the like, and supplies a phase and b phase voltages from voltage supply means (power source 104 shown in FIG. 4). is doing.

  In the configuration of FIG. 4, the electrodes have two phases, the odd-numbered electrodes are a phase and the even-numbered electrodes are b phase. FIG. 7 shows voltages applied to the a phase and the b phase. The voltage is a rectangular wave, Vpp is 200 V to 1000 V, the frequency f is 0.1 to 5 kHz, and the central value V0 of the voltage varies between the image portion potential and the non-image portion potential depending on the development conditions. The a-phase and b-phase voltages are applied with a phase shift of π. Due to this phase difference, there is always a potential difference of Vpp between the a phase and the b phase. Due to this potential difference, an electric field is generated between the electrodes, and the toner hops between the electrodes in accordance with the electric field. In FIG. 7, the applied voltage is a rectangular wave. However, in the case of a rectangular wave, voltage switching occurs instantaneously and is suitable for toner hopping. However, the voltage waveform is not limited to a rectangular wave, and a sine wave or a triangular wave is also possible. But you can.

  In the developing device 13 shown in FIG. 3, in addition to the above-described configuration, the downstream portion of the toner regulating member 13c in the toner transport direction of the first toner carrier 13A is adjacent to the first toner carrier 13A. The second toner carrier 13B is installed in a developing portion (development area) for developing the electrostatic latent image on the image carrier 11.

If the second toner carrier 13B is not in contact with the image carrier 11, a hard metal roller such as Al, stainless steel, or Cu can be used. Further, a roller formed of an elastic body such as a rubber material may be used. As the rubber material, natural rubber, silicone rubber, urethane rubber, fluorine rubber, ethylene-propylene rubber, butyl rubber and the like can be widely used. In addition, for the purpose of realizing durability improvement such as improvement of wear resistance, improvement of image quality by electroconductivity, development with a low potential latent image and a low potential bias voltage, the rubber material is made of TiO ₂ , Fe ₂ O ₃ , SiO _{2. 2} , inorganic compound fine powder such as SnO ₂ , whiskers such as NaTiO ₂ , carbon black and the like may be included.

  Further, the surface of the second toner carrier 13B has a reliable toner transportability and transport stability, uniformity of the formed toner thin layer and toner thin layer uniformity, prevention of toner filming, and surface layer wear. For the purpose of improving image quality and durability, such as prevention, a resin layer convenient for at least the surface portion may be provided. Examples of the material of the resin layer include organic polymer compounds, organic polymer compounds containing organic low molecular compounds, thermosetting resins, organic compounds and resins containing carbon black, organic compounds and resins containing inorganic compound fine particles, and the like. Can be used.

  Further, in the developing device 13 shown in FIG. 3, a toner storage portion 13g for storing toner for use in development is provided in a region of the developing casing 13e opposite to the image carrier 11 of the toner supply roller 13h. A paddle 13d, which is a toner agitating member for pumping the toner in the toner storage portion 13g to the toner supply roller 13h while being agitated, is installed.

The first toner carrier 13A in FIG. 3 is rotated clockwise by a rotation driving device (not shown). The second toner carrier 13B is preferably rotated in the traveling direction of the image carrier 11 by a rotation driving device (not shown), but may be in a direction opposite to the traveling direction of the image carrier 11.
The toner supplied to the first toner carrier 13A by the toner supply roller 13h is thinned and frictionally charged by the toner regulating member 13c, and then between the electrodes formed on the surface of the first toner carrier 13A. A cloud is formed by the electric field, and is carried to the vicinity of the second toner carrier 13B.

Since the toner carried to the vicinity of the second toner carrier 13B is supplied to the second toner carrier 13B while forming a cloud, only the charged toner is supplied from the first toner carrier 13A to the second toner carrier 13B. The toner can be supplied and carried on the second toner carrier 13B. Therefore, it is not necessary to frictionally charge the toner on the second toner carrier 13B with a contact member such as a thinning blade, and development characteristics due to toner filming on the second toner carrier 13B or wear of the contact member. This eliminates problems such as image unevenness due to changes over time, and contact members such as thinning blades that have been in contact for a long time when not in operation.
The toner transferred to the second toner carrier 13B in this way is carried to a development area that is a portion facing the image carrier 11, and the electrostatic latent image on the image carrier is developed.

  As described above, in the developing device 13 of the present embodiment, the toner is vibrated and charged by the first toner carrier 13A having the electric field generating member for forming the cloud, so that the toner on the second toner carrier 13B is charged. Since there is no need to provide a contact member for frictionally charging the toner, there are problems such as toner filming on the second toner carrier 13B and changes in development characteristics over time due to wear of the toner carrier and the contact member. Absent. Further, since a two-component developer is not used, it is not necessary to periodically replace a deteriorated carrier.

[Example 2]
Next, an embodiment of the second means will be described with reference to FIG.
In the developing device 13 of the present embodiment, in addition to the configuration of the first embodiment, the first toner carrier 13A and the second toner carrier 13B form a non-contact gap of about 50 to 500 μm, There is no contact of the member with the second toner carrier 13B.
In this embodiment, the toner supply potential ΔVsup is set to 150 V or less, and the linear speed ratio of the first toner carrier 13A to the second toner carrier 13B is set to 2.5 or more. An electric field is formed between the first toner carrier 13A and the second toner carrier 13B by a potential difference (toner replenishment potential) due to a bias voltage applied to both rollers. Unless the toner supply potential ΔVsup is set to 150 V or less, if the second toner carrier 13B is operated in an undeveloped state, the amount of toner attached on the second toner carrier 13B will increase. In this case, the toner supply capability to the second toner carrier 13B after consumption of the solids is inevitably reduced. To compensate for this, the line of the first toner carrier 13A with respect to the second toner carrier 13B is compensated. It is effective to increase the speed ratio.

[Example 3]
Next, an embodiment of the third means will be described.
In addition to the configuration of the first or second embodiment, the developing device 13 of the present embodiment supplies voltage to the electrode of the first toner carrier 13A and voltage to the second toner carrier 13B. A common voltage supply means is used.

  The electrode configuration of the first toner carrier 13A in FIG. 3 is two-phase, the odd-numbered electrodes are a-phase, the even-numbered electrodes are b-phase, and the voltages of the a-phase and b-phase are shifted by π. Applied. Due to this phase difference, there is always a potential difference of Vpp between the a phase and the b phase. Due to this potential difference, an electric field is generated between the electrodes, and the toner hops between the electrodes according to the electric field to form a cloud.

FIG. 8A shows voltages applied to the a phase and b phase of the first toner carrier 13A, and FIG. 8B shows voltages applied to the second toner carrier 13B. In this example, the voltage applied to the a phase of the first toner carrier 13A is the same as the voltage applied to the second toner carrier 13B. Thus, the a phase of the first toner carrier 13A is the same. By applying the voltage of either the b phase or the b phase to the second toner carrier 13B, a potential difference is generated between the first toner carrier 13A and the second toner carrier 13B, and an electric field is generated. Therefore, a part of the toner that alternately moves between the a phase and the b phase moves to the second toner carrier 13B.
In FIG. 8, the applied voltage is a rectangular wave, but in the case of a rectangular wave, voltage switching occurs instantaneously and is suitable for toner hopping. However, it is not limited to a rectangular wave, and may be a sine wave or a triangular wave. .

[Example 4]
Next, an embodiment of the fourth means will be described.
In the developing device 13 of the present embodiment, in addition to any one of the configurations of the first to third embodiments, the first toner carrier 13A having a plurality of electrodes, as shown in FIG. Casing) 13e is housed inside.

The first toner carrier 13A has a surface protective layer 103 formed of an inorganic or organic insulating material that serves as a protective film covering the electrode surface. In particular, in the case of a surface protective layer of a polymer insulating material, The moisture resistance is absorbed and the volume resistance changes. In the first toner carrier 13A, since the electrode interval between the plurality of electrodes is as narrow as several tens of microns, even a slight change in volume resistance affects the cloud electric field.
Therefore, in order to prevent moisture in the air from being absorbed, the first toner carrier 13A is housed in the developing casing 13e as shown in FIG. 3, and is near the developing opening of the second toner carrier 13B. In this case, a seal 13i is provided so that the seal 13i comes into light contact with the second toner carrier 13B to block the inside of the developing casing 13e from outside air. Thus, in the present embodiment, the first toner carrier 13A is sealed inside the developing casing 13e, and thus is not easily affected by the humidity of the outside air.

[Example 5]
Next, an embodiment of the fifth means will be described.
In the developing device 13 of the present embodiment, the second toner carrier 13B and the image carrier 11 are in a non-contact configuration in addition to any of the configurations of the first to fourth embodiments.
That is, in this embodiment, a non-contact development method is used in which development is performed without bringing the toner on the second toner carrier 13B into contact with the surface of the image carrier 11, and in the non-contact development method, the second Since the toner carrier 13B does not contact the surface of the image carrier 11, the second toner carrier 13B can be formed of a relatively hard metal material having a hardness of 70 ° or more. When the non-contact development method is employed, the distance between the second toner carrier 13B and the image carrier 11 is set within the range of the toner layer thickness to 150 μm.

  The surface layer coating material of the second toner carrier 13B may have a polarity opposite to that of the toner, or may have the same polarity when the toner does not have a function of frictionally charging the toner to a desired polarity. Examples of the former surface layer coating material include materials containing a resin, such as silicon, acrylic, and polyurethane, and rubber. In addition, examples of the latter surface layer coating material include a material containing fluorine. A so-called Teflon (registered trademark) material containing fluorine has a low surface energy and excellent releasability, and therefore toner filming with time is extremely difficult to occur. Also, as general resin materials that can be used for the surface layer coating material, polytetrafluoroethylene (PTFE), tetrafluoroethylene perfluoroalkyl vinyl ether (PFA), tetrafluoroethylene / hexafluoropropylene polymer (FEP) , Polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene / ethylene copolymer (ETFE), chlorotrifluoroethylene / ethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), etc. Can be mentioned. In order to obtain conductivity, a conductive material such as carbon black is often contained as appropriate. Further, other resins may be mixed so that the toner carrier 13B can be coated uniformly. Regarding electrical resistance, the volume resistivity of the bulk including the coat layer is set. The resistance and adjustment of the base layer are adjusted so that it can be set to 10 ^ 3 [Ω · cm] or more and 10 ^ 8 [Ω · cm] or less. Do. Since the volume resistivity of the base layer used in this embodiment is not less than 10 3 [Ω · cm] and not more than 10 5 [Ω · cm], the volume resistivity of the surface layer may be set slightly higher. However, when the non-contact development method is adopted, there is little fear of charge leakage due to contact, so it is possible to set the volume resistivity to less than 10 ^ 3 [Ω · cm] in order to increase the electric field strength. is there.

[Example 6]
Next, an embodiment of the image forming apparatus of the sixth and seventh means will be described.
The basic configuration and operation of the image forming apparatus of this embodiment are the same as those in FIG. 1, and are as described above. In the image forming apparatus of this embodiment, each color developing device (developing cartridge) 13K, 13M, 13C, 13Y includes the developing device 13 having the configuration shown in FIG. The configuration is as described in the first to fifth embodiments.
In this embodiment, since the developing device having the configuration described in Embodiments 1 to 5 is provided, good and stable image formation can be performed. Further, as shown in FIG. 1, each color developing device (developing cartridge) 13K, 13M, 13C, 13Y is provided with the developing device 13 having the configuration shown in FIG. It can be carried out.

[Example 7]
Next, an embodiment of the image forming apparatus of the eighth and ninth means will be described.
In this embodiment, as a process cartridge installed in an image forming apparatus that forms an image by an electrophotographic process, at least the developing device 13 of any one of Embodiments 1 to 5 is provided in the cartridge, and is attached to and detached from the image forming apparatus. This is possible.

  Here, in this embodiment, the “process cartridge” is a cartridge that is integrally configured including at least the developing device 13 and is detachable from the main body of the image forming apparatus. That is, the developing cartridge 13 shown in FIG. 3 can also be regarded as a kind of process cartridge. In the configuration example of FIG. 9, the developing cartridge 13 shown in FIG. 3 is replaced with black, magenta, cyan, respectively. The process cartridges 13K, 13M, 13C, and 13Y for forming yellow toner images are used. In the process cartridges 13K, 13M, 13C, and 13Y, as shown in FIG. 9, the image carrier 11 is a roller 11c. By pivoting and retracting downward with the fulcrum as a fulcrum, it can be detached from the open space and can be easily replaced by the user.

  In the above description, the developing cartridge 13 is regarded as a kind of process cartridge. However, the developing device 13 and the charging device 12 shown in FIG. 3 may be integrated into a process cartridge.

In the example of FIGS. 1 and 9, a belt-like photoconductor is used as the image carrier 11, and a plurality of color toner images are formed on the image carrier. However, instead of this configuration, A member denoted by reference numeral 11 is an intermediate transfer belt, and a drum-shaped photoconductor is disposed between the intermediate transfer belt and each of the developing cartridges 13K, 13M, 13C, and 13Y, and a toner image of each color is formed on each photoconductor. Thereafter, the image can be transferred onto the intermediate transfer belt (not shown). In the case of such a configuration, each developing cartridge, the photosensitive member, and the charging device (and a cleaning member if necessary) can be configured integrally to form a process cartridge.
In other words, in this configuration, the developing cartridge 13 having the configuration shown in FIG. 3, the photosensitive member (not shown), and the charging device 12 are integrated to form a process cartridge, and four process cartridges are arranged along the intermediate transfer belt. At the time of image formation, the writing devices 14K, 14M, 14C, and 14Y irradiate the photoconductors of the process cartridges with writing light corresponding to the image information of black, magenta, cyan, and yellow, respectively. The process cartridge develops a latent image corresponding to the writing light with the toner of the developing device 13 to form a toner image on each photoconductor, and transfers the toner image on the intermediate transfer belt in an overlapping manner. The toner image transferred to the intermediate transfer belt is transferred to the transfer material by the transfer roller 16, and the toner image on the transfer material is fixed by the fixing device 17.

The configuration example of the image forming apparatus of the present invention has been described above. However, the image forming apparatus to which the present invention can be applied is not particularly limited as long as the developing cartridge of the present invention and the process cartridge including the same can be attached and detached. In addition to the structure of a direct transfer type color image forming apparatus using such a photoreceptor belt and an intermediate transfer type color image forming apparatus using an intermediate transfer belt, color images using a transfer drum, an intermediate transfer drum, etc. Needless to say, the present invention can also be applied to a forming apparatus, a direct transfer type color image forming apparatus using a transfer material conveying belt, or a monochrome image forming apparatus.
In the present invention, the electric field generating member that performs electrostatic conveyance is applied to the toner carrier. However, the object that is electrostatically conveyed by the electric field generating member is not limited to toner, and can be applied to powders in general.

1 is a schematic configuration diagram illustrating a configuration example of an image forming apparatus to which the present invention is applicable. FIG. 2 is a schematic configuration diagram illustrating an example of a developing cartridge used in the image forming apparatus in FIG. 1. 1 is a schematic configuration diagram of a developing device (developing cartridge) showing an embodiment of the present invention. FIG. 3 is an enlarged partial sectional view of a surface of an electric field generating member of a first toner carrier. FIG. 3 is a perspective view illustrating an appearance of a first toner carrier. (A) is a diagram showing a cross-sectional configuration example of the first toner carrier, and (b) is a diagram of the first toner carrier as viewed from a direction parallel to the axis. FIG. 4 is a diagram illustrating an example of voltages applied to a phase and b phase of a first toner carrier. FIG. 4 is a diagram illustrating an example of a voltage applied to a phase and a b phase of a first toner carrier and a voltage applied to a second toner carrier. 1 is a schematic configuration diagram illustrating a configuration example of an image forming apparatus to which the present invention is applied.

Explanation of symbols

10: image forming apparatus 11: image carrier 12 (12K, 12M, 12C, 12Y): charging device 13 (13K, 13M, 13C, 13Y): developing device (developing cartridge)
13A: First toner carrier 13B: Second toner carrier 13c: Toner regulating member 13d: Paddle (toner stirring member)
13e: Development casing 13g: Toner storage unit 13h: Toner supply roller (toner supply means)
13i: Seal 14 (14K, 14M, 14C, 14Y): Writing device 15: Paper feeding device 16: Transfer roller 17: Fixing device 18: Paper discharge tray

Claims (9)

In a developing device that develops an electrostatic latent image on an image carrier with a toner to make a visible image,
A toner carrier having a plurality of electrodes therein, and a voltage supply means for supplying a voltage to the electrodes so that the electric field between the electrodes changes temporally, and the electric field between the electrodes A first toner carrier having an electric field generating member that is separated from the surface of the toner carrier to form a cloud;
Toner supply means for supplying toner to the surface of the electric field generating member of the first toner carrier;
A toner regulating member that regulates a toner layer on the surface of the electric field generating member of the first toner carrier;
A toner storage for storing toner for use in development;
A toner agitating member for agitating the toner in the toner storage unit,
A developing device, wherein a second toner carrier is provided in a developing unit for developing an electrostatic latent image on the image carrier in the vicinity of the first toner carrier. The developing device according to claim 1,
The developing device according to claim 1, wherein the first toner carrier and the second toner carrier are not in contact with each other. The developing device according to claim 1 or 2,
2. A developing device according to claim 1, wherein a voltage supply means for supplying a voltage to the electrode of the first toner carrier and a voltage supply means for supplying a voltage to the second toner carrier are common. The developing device according to any one of claims 1 to 3,
The developing device according to claim 1, wherein the first toner carrier having the plurality of electrodes is stored in a developing device casing. In the developing device according to any one of claims 1 to 4,
The developing device, wherein the second toner carrier and the image carrier are not in contact with each other. In an image forming apparatus for developing an electrostatic latent image on an image carrier with a toner to make a visible image, and finally transferring the toner image on the image carrier to a recording material to form an image.
An image forming apparatus comprising the developing device according to claim 1 as means for developing an electrostatic latent image on the image carrier. The image forming apparatus according to claim 6.
An image forming apparatus comprising a plurality of the developing devices, wherein an image obtained by superimposing a plurality of toner images on the image carrier is transferred to the recording material to form a multicolor or full color image. A process cartridge installed in an image forming apparatus that forms an image by an electrophotographic process,
A process cartridge comprising at least the developing device according to claim 1, wherein the process cartridge is detachably attached to the image forming apparatus. An image forming apparatus that forms an image by an electrophotographic process,
9. An image forming apparatus comprising a single or a plurality of process cartridges according to claim 8 for forming a single color, multicolor or full color image.

Images