JP2007086694A - Developing device, image forming process unit, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To lower the wear of a toner carrier and to strengthen durability by restricting and controlling a slidingly rubbing conditions of a magnetic brush for making a two-component developer slidingly rub the toner carrier when separating only the toner from the two-component developer and supplying the developer to the toner carrier. <P>SOLUTION: A developing device (developing means) 14 includes the toner carrier 402 which carries the toner 10 and conveys the toner 10 to a photoreceptor 1, and a toner supplying member 403 which conveys the two-component developer 12 to the toner carrier 402 and supplies only the toner 10 by the two-component developer 12 to the toner carrier 402. Also, the development device 4 uses the two-component developer 12 having the carrier grain size greater than the toner grain size; the magnetic flux density of the magnetic pole at which the toner supplying member 403 causes the two-component developer 12 to nap is ≥50 mT and ≤123 mT on the surface of the toner supplying member 403 and the saturation magnetization of the magnetic particles is ≥35 emu/g and ≤l30 emu/g. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a developing device, an image forming process unit, and an image forming device, and in particular, includes a toner carrier that carries toner on its surface and conveys it to a development region opposite to a latent image carrier, and toner and magnetic particles. A developing device having a toner supply member that carries a component developer, conveys the toner to a toner supply region facing the toner carrier, and supplies only the toner from the two-component developer to the toner carrier; The present invention relates to an image forming process unit and an image forming apparatus.

  Conventionally, as a developing device used in an image forming apparatus, a two-component developing device that develops an electrostatic latent image on a latent image carrier using a two-component developer containing toner and magnetic particles, and one-component development of toner A one-component developing device that develops an electrostatic latent image on a latent image carrier using an agent is known. Among these developing devices, the latter one-component developing device has an advantage that the configuration is simple and the size can be reduced. Further, since magnetic particles are not used, a phenomenon in which development unevenness occurs somewhat in the electrostatic latent image due to the state in which the magnetic brush of the two-component developer hits the latent image carrier, so-called magnetic brush marks do not occur. Furthermore, the developer layer is thinner than the former two-component developing device, and there is less phenomenon called the edge effect. For this reason, the one-component developing device is excellent in reproducibility of high-definition images. Among them, a developing device using a non-magnetic one-component developer is suitable as a developing device that obtains a high-definition color image because it is excellent in colorization.

  However, in a normal one-component developing device, toner charge control on the toner carrying member is performed by frictional charging with a contact member such as a blade or a toner supply roller that contacts the toner carrying member. There is a problem that it is difficult to cope with the increase in durability and durability.

  In addition, the toner on the toner carrying member is stressed by the pressurization of the contact member, causing toner filming, or external additives entering the toner, which may cause deterioration in image quality. . In addition, the friction between the toner carrying member and the contact member may cause both to wear and change the development characteristics over time.

  In order to solve these problems, it is considered preferable to supply and carry toner charged to a predetermined polarity on a toner carrier without using frictional charging by a contact member such as the blade or toner supply roller described above. It is done.

  For this reason, for example, in Patent Documents 1 and 2, a two-component developer is used as a developing device that can supply and carry toner charged to a predetermined polarity on a toner carrier without using frictional charging by the contact member. A developing device has been proposed in which a toner supply member having a magnetic brush formed on the surface thereof is used and only toner is supplied to the toner carrier from the magnetic brush on the toner supply member.

  In these developing devices, a two-component developer is carried on a toner supply member (magnet 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).

For example, Patent Document 3 proposes a method in which the developing device is limited to a carrier diameter smaller than the toner diameter.
JP 56-40862 A JP 59-172626 A JP 2003-228229 A

  However, the method of Patent Document 1 or 2 has a problem that the toner carrier is rubbed with a magnetic brush and is not as durable as the mechanical life.

  Further, in the method of Patent Document 3, the carrier diameter is limited to be smaller than the toner diameter, but the main purpose is prevention of toner scattering and carrier adhesion, and no mention is made regarding durability.

  At this time, in order not to generate an afterimage, the rotation direction of the toner supply member and the toner carrier is reversed, and the linear speed ratio (toner supply member speed / toner carrier speed) of the toner supply member and the toner carrier is set to 2. Need to be higher. Since the speed of the toner supply member is thus large, the frequency with which the magnetic brush contacts the developing roller is increased.

  Therefore, the present invention has been made in consideration of the above-described circumstances. When only the toner is separated from the two-component developer and supplied to the toner carrier, the two-component developer is rubbed against the toner carrier. An object of the present invention is to limit the rubbing conditions of the magnetic brush and reduce the wear of the toner carrying member to enhance the durability.

  In order to solve the above-mentioned problem, the invention according to claim 1 is a developing device, wherein a toner carrying member that carries toner on a surface thereof and conveys the toner to a developing region facing the latent image carrying member, and the toner A two-component developer containing a carrier of magnetic particles is carried, the two-component developer is conveyed to a toner supply region facing the toner carrier, and only the toner from the two-component developer is transferred to the toner carrier. A toner supply member having a magnetic field generating means for causing the two-component developer to rise, and the two-component developer has a particle size of the carrier larger than the particle size of the toner, The magnetic flux density of the magnetic pole for causing the component developer to rise is 50 mT or more and 120 mT or less on the surface of the toner supply member, and the saturation magnetization of the carrier is 35 emu / g or more and 130 emu / g or less. And wherein the Rukoto.

  According to a second aspect of the present invention, in the developing device according to the first aspect, a nip width at which the toner carrier and the two-component developer are in contact with each other is 0.5 mm or more and 3 mm or less.

  According to a third aspect of the present invention, in the developing device according to the first or second aspect, the height of the raised developer from the surface of the toner supply member is such that the toner supply member and the toner carrier are opposed to each other. It is characterized by being not more than twice the distance to the surface.

  According to a fourth aspect of the present invention, in the developing device according to any one of the first to third aspects, the carrier and the toner carrier when the developer spikes and contacts the toner carrier. The toner is interposed between the two.

  According to a fifth aspect of the present invention, in the developing device according to any one of the first to fourth aspects, the distance between the toner carrier and the toner supply member is five times the average particle diameter of the magnetic particles. It is characterized by being 20 times or less.

  According to a sixth aspect of the present invention, in the developing device according to any one of the first to fifth aspects, the developing device includes a photosensitive member, and the non-image portion potential of the photosensitive member is set to VD and exposure is performed. When the partial potential is VL and the developing bias voltage is VB, 0 <| VD | − | VB | <| VD−VL | <250V is satisfied.

  According to a seventh aspect of the present invention, in the image forming process unit, one or more devices selected from a charging device for uniformly charging the surface of the latent image carrier and a cleaning device for the surface of the latent image carrier; An image forming process unit in which a latent image carrier and a developing device for developing a latent image on the latent image carrier are configured to be detachable from the image forming apparatus as an integral structure, A developing device according to any one of claims 1 to 6 is used.

  In the image forming apparatus, the toner image on the latent image carrier is transferred to the intermediate transfer member, and the toner image on the latent image carrier is transferred to the intermediate transfer member. A secondary transfer device, a secondary transfer device that transfers a toner image on the intermediate transfer member onto a transfer material, and an image forming process unit according to claim 7.

  According to the present invention, it is possible to reduce the rubbing force between the developer and the developing roller, and to prevent the developing roller (toner carrier) from being deteriorated due to rubbing of the developer. Further, the carrier is prevented from coming into direct contact with the developing roller (toner carrier) by the presence of toner, and the durability of the developing roller (toner carrier) is improved, thereby improving the durability of the image forming apparatus and The durability of the body is improved and the durability of the image forming apparatus is improved.

  Hereinafter, a developing device and the like according to an embodiment of the present invention will be described with reference to the drawings.

<Embodiment 1>
First, a developing device according to an embodiment of the present invention will be described.

  As shown in FIG. 1, a developing roller (toner carrier) 402 as a toner carrier, a magnetic brush roller 403 as a toner supply member, an agitator Conveying members 404 and 405 are provided. A two-component developer (hereinafter simply referred to as “developer”) 12 containing the toner 10 and magnetic particles 11 in the casing 401 is agitated by the agitating / conveying members 404 and 405, and a part thereof is a magnetic brush roller. It is carried on 403. The developer 12 on the magnetic brush roller 403 comes into contact with the developing roller (toner carrier) 402 in the toner supply region A2 after the layer thickness is regulated by a regulating blade 406 as a developer regulating member. In this toner supply region A 2, only the toner 10 is separated from the developer 12 on the magnetic brush roller 403 and supplied to the developing roller (toner carrier) 402.

  In the developing device of this embodiment, since the rigid drum-shaped photosensitive member 1 based on an aluminum base tube is used, the developing roller (toner carrier) 402 is preferably a rubber material. And the range of 10-70 degrees (JIS-A) is suitable for the hardness, and the range whose diameter is 10-30 mm is suitable. In this embodiment, the developing roller 402 having a diameter of 16 mm is used. The surface of the developing roller 402 is appropriately roughened, and its roughness Rz (10-point average roughness) is 1 to 4 μm. The range of the surface roughness Rz is about 13 to 80% with respect to the volume average particle diameter of the toner 10, and is a range in which the toner 10 is conveyed without being buried in the surface of the developing roller (toner carrier) 402. . Here, examples of the rubber material of the developing roller (toner carrier) 402 include rubbers or elastomers such as silicon, butadiene rubber, NBR, hydrin rubber, and EPDM. Further, when a so-called belt photoconductor is used, it is not necessary to lower the hardness of the developing roller 402, so a metal roller or the like can also be used.

  The surface of the developing roller (toner carrier) 402 is preferably coated with a coating material as appropriate in order to stabilize the quality with time. Further, the developing roller (toner carrier) 402 in this embodiment is for carrying toner, and as in the conventional one-component developing device, charging charge is applied to the toner 10 by frictional charging between the toner 10 and the developing roller 402. Therefore, the developing roller 402 only needs to satisfy electric resistance, surface property, hardness, and dimensional accuracy, and the selection range of materials is remarkably increased.

The surface layer coating material of the developing roller 402 may be charged with a polarity opposite to that of the toner 10 or may be the same polarity when the toner is not given 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 fluororesin (Teflon (registered trademark))-based material containing fluorine has low surface energy and excellent releasability, so that toner filming hardly occurs over time. Further, as general resin materials that can be used for the surface layer coating material, polytetrafluoroethylene (PTFE), tetrafluoroethylene perfluoroalkyl vinyl ether (PFA), tetrafluoroethylene / hexafluoropropylene copolymer ( FEP), polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene / ethylene copolymer (ETFE), chlorotrifluoroethylene / ethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF) And the like. In order to obtain conductivity, these resin materials often contain a conductive material such as carbon black as appropriate. Further, other resins may be mixed so that the developing roller 402 can be uniformly coated. Regarding electric resistance, the volume resistivity of the bulk including the coat layer is set, and the resistance and adjustment of the base layer are performed so that it can be set in a range of 10 ³ to 10 ⁸ Ω · cm. Since the volume resistivity of the base layer used in this embodiment is in the range of 10 ³ to 10 ⁵ Ω · cm, the volume resistivity of the surface layer may be set slightly higher.

  Magnetic particles used as carriers include ferromagnetic metals such as iron, cobalt and nickel, metal oxides such as magnetite, magnetic materials such as ferrite, or magnetic materials such as ferrite having a resin core. Can be used. The particle size is preferably in the range of 20 to 60 μm.

As such a carrier, for example, binder type particles (1 to 10 μm, 2 to 3 × 10 ¹³ Ω · cm or more, 20 to 50 emu / g) in which a fine powder magnetic material such as magnetite is dispersed in a resin are used as carriers. A core material having a metal film on the surface can be used. The carrier core material composed of the binder-type particles has many characteristics such as low magnetic force, small specific gravity, high electric resistance, and small particle size. In addition, since a wide range of characteristics can be obtained by selecting materials and adjusting the composition ratio, it can be said that it is suitable for high-quality carriers.

Ferrite powders (1 to 10 μm, 4.5 to 5.5 × 10 ⁶ to 10 ¹⁵ Ω · cm, 40 to 70 emu / g) include ferrite powders such as copper, nickel, zinc, cobalt, manganese, and magnesium. Used. This ferrite-based carrier is easy to adjust the physical properties such as magnetic force and electrical resistance depending on the composition and manufacturing conditions, and has the characteristics that it is spherical, has good fluidity, and is chemically stable. It can be said that it is suitable for extending the service life.

Iron powder carriers (1 to 10 μm, 7 to 8 × 10 ⁹ Ω · cm or less, 70 to 250 emu / g) are classified into reduced iron powder, atomized iron powder, iron nitride powder, and the like depending on the production method. Since reduced iron powder and iron nitride powder are indefinite, they may be spheroidized. The iron powder carrier has been previously oxidized.

The developing device of the present embodiment has a photoconductor, and when the non-image portion potential of the photoconductor is VD, the exposure portion potential is VL, and the development bias voltage is VB, the following equation (1) is obtained. It is characterized by satisfying.
0 <| VD | − | VB | <| VD−VL | <250 V (1)
This imposes such conditions in order to reduce the amount of energized charge of the photoreceptor 1, reduce fatigue of the photoreceptor due to repeated charging and exposure of the photoreceptor 1, and extend the life of the photoreceptor 1. Is.

  In this embodiment, the non-image portion potential (potential of the portion of the photoconductor charged by the charging means) VD, the latent image portion potential (portion of the photoconductor charged by the charging portion (light exposure portion) written by optical writing). Potential) VL and development bias potential VB are set to -350 [V], -50 [V], -250 [V], that is, development potential 200 [V] (VL-VB = 200), respectively. Is going. However, under this development condition, the difference between VD and VB is small, so that the toner tends to adhere to the background, and image defects such as background stains are likely to occur. Therefore, when this development condition is used, as described above, the amount of reversely charged toner that passes through the opening per unit time is set to 200 [g · mm / min] or less, so that the fog image caused by toner scattering is obtained. Can be effectively suppressed.

  Further, when the non-image portion potential of the photoreceptor 1 is VD, the latent image portion potential (exposure portion) potential is VL, and the developing bias voltage applied to the photoreceptor 1 is VB, the above equation (1) is satisfied, and If the minimum adhesion amount X that can obtain the image saturation density is set, the maximum adhesion amount on the photosensitive member is set to 1.5 × X or less. Here, the minimum adhesion amount X is expressed as X = particle size × true specific gravity / transfer rate × 0.6 as an adhesion amount in which at least 60% of the toner exists in a space corresponding to the thickness depending on the toner particle size. By satisfying such conditions, the amount of electrified charge of the photosensitive member 1 is reduced, the fatigue of the photosensitive member due to repeated charging / exposure to the photosensitive member 1 is reduced, and the life of the photosensitive member 1 can be extended. .

  Hereinafter, the embodiment of the present invention will be described in detail by way of examples. However, numerical values or configuration examples described in the embodiments are exemplifications, and the present invention should not be construed as being limited to these specific numerical values or configuration examples. It will be construed in its entirety disclosed in the drawings.

  FIG. 2 shows the relationship between the magnetic flux density of the magnetic pole to be raised and the saturation magnetization of the magnetic particles in the developing device of this embodiment.

  If the magnetic flux density to be supported exceeds 120 mT, the hardness of the magnetic brush is increased and the developing roller is damaged. Further, when the magnetic flux density to be spiked is less than 50 mT, the carrier holding force becomes weak, the carrier adheres frequently, and the developer does not pass through the supply nip.

  Similarly, when the saturation magnetization of the magnetic particles is 35 emu / g or less, carrier adhesion occurs frequently, causing problems such as the developer no longer passing through the supply nip. On the other hand, if it exceeds 130 emu / g, the hardness increases and Damage is caused, causing problems such as brush marks on the supply section. For this reason, the range as shown in FIG. 2 is appropriate as the range of the magnetic flux density of the magnet to be raised and the saturation magnetization of the magnetic particles.

  When the height of the raised magnetic brush in the supply nip exceeds twice the distance (supply gap) between the toner carrier and the toner supply member, a developer that cannot pass through the supply nip is generated. The developer may accumulate in front of the part. For this reason, the height of the heading is preferably not more than twice the supply gap. Moreover, in order to suppress the height of the spike, it can be achieved by setting the magnetic flux density of the magnetic pole to be raised to 120 mT or less.

  When the carrier comes into direct contact with the developing roller, the carrier surface having high hardness damages the developing roller, and the durability of the developing roller is lowered. Therefore, it is necessary that toner that is a soft resin always exists on the surface of the carrier. In order for the carrier not to directly touch the developing roller, the toner coverage of the carrier needs to be 50% or more.

  FIG. 3 shows the durability of the developing device of this embodiment and the conventional developing device.

As an experimental device, a modified machine of imgio Color-5100 is equipped with the developing device of this embodiment, and a ferrite carrier (saturation magnetization 60 emu / g, diameter 50 μm) and toner (negatively charged toner, average particle diameter 6.8 μm). Further, the durability was examined using an applied bias as a supply roller bias of −150 V and a developing roller bias of −75 V, and using the toner adhesion amount on the developing roller as an index. The toner adhesion amount is preferably 0.45 mg / cm ² or more, the image density decreases when becomes less.

<Comparative Example 1>
On the other hand, Comparative Example 1 uses an iron powder carrier (saturation magnetization 150 emu / g, diameter 50 μm) and toner (negatively charged toner, average particle diameter 6.8 μm). Further, in the case of using the carrier having a large saturation magnetization of Comparative Example 1, streaks due to the traces of the magnetic brush are also generated during solid development.

  FIG. 4 shows the durability when the nip width is changed. Durability was evaluated by the same amount of adhesion as in the previous embodiment.

  When the nip width is wide, the developer hitting the developing roller increases, so the time for the magnetic brush to hit the developing roller increases. The durability starts to drop when the nip width is 3 mm or more, and conversely starts to rise when the nip width is 1 mm or less. However, when the nip width is 0.5 mm or less, the toner supply capability is reduced, and sufficient toner cannot be secured on the developing roller, so that the toner development amount during solid development cannot be secured. The force exerted on the developing roller by the carrier can be reduced by shortening the length of the magnetic brush head.

  If the distance (supply gap) between the developing roller and the toner supply member is narrow and not more than 5 times the average particle size of the magnetic particles, the carrier is rubbed strongly, so that the durability of the developing roller is deteriorated. If it is twice or more, a sufficient amount of toner cannot be supplied.

<Embodiment 2>
Next, an image forming apparatus according to an embodiment of the present invention will be described.

  FIG. 5 is a diagram showing a schematic configuration of the image forming apparatus of the present embodiment. The photoconductor 1, the charging unit 2, the charge eliminating unit 3, the developing unit 4, the transfer roller, the fixing unit 6, and the cleaning unit 7 are included.

  The developing unit 4 uses the developing device of the first embodiment. Since the developing device has improved durability, replacement by maintenance can be reduced and resource saving can be achieved. Further, the potential applied to the photosensitive member 1 can be lowered by contact development with the developing means 4. As a result, the photosensitive member 1 has a long life, and the maintenance cost can be reduced.

<Embodiment 3>
Next, the image forming process unit according to the embodiment of the present invention will be described.

  FIG. 6 is a diagram showing a schematic configuration of the image forming process unit of the present embodiment. The image forming process unit 8 includes a photoreceptor 1, a charging unit 2, a developing unit 4, and a cleaning unit 7.

  The developing unit 4 uses the developing device of the first embodiment. As shown in FIG. 6, the maintainability of the image forming apparatus can be improved by making the developing device of the first embodiment, the photoconductor and the like into one replaceable unit.

  The above-described embodiment is a preferred embodiment of the present invention, and the scope of the present invention is not limited to the above-described embodiment alone, and various modifications are made without departing from the gist of the present invention. Implementation is possible.

1 is a cross-sectional view illustrating a configuration of a developing device according to an embodiment of the present invention. It is explanatory drawing which shows the range of the saturation magnetization of the magnetic particle used in embodiment of this invention, and the magnetic flux density of a main pole. It is explanatory drawing which shows durability of the developing device of the developing device which concerns on embodiment of this invention. It is explanatory drawing which shows durability at the time of nip width change of the developing device of the developing device which concerns on embodiment of this invention. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. 1 is a schematic configuration diagram of an image forming process unit according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging means 3 Static elimination means 4 Developing means 5 Transfer roller 6 Fixing means 7 Cleaning means 8 Image forming process unit 10 Toner 11 Magnetic particle 12 Two-component developer 401 Casing 402 Developing roller (toner carrier)
403 Magnetic brush roller 404, 405 Stirring / conveying member 406 Regulating blade

Claims (8)

A toner carrier that carries toner on a surface thereof and conveys the toner to a development region facing the latent image carrier;
A two-component developer containing the toner and a carrier of magnetic particles is carried, the two-component developer is transported to a toner supply region facing the toner carrier, and only the toner is transferred from the two-component developer. A toner supply member having a magnetic field generating means for causing the two-component developer to rise so as to be supplied to the carrier,
The two-component developer has a particle size of the carrier larger than the particle size of the toner, and a magnetic flux density of a magnetic pole for causing the two-component developer to rise is 50 mT or more and 120 mT or less on the surface of the toner supply member. And a saturation magnetization of 35 emu / g or more and 130 emu / g or less.   The developing device according to claim 1, wherein a nip width in which the toner carrying member and the two-component developer are in contact with each other is set to 0.5 mm or more and 3 mm or less.   3. The height of the raised developer from the surface of the toner supply member is not more than twice the distance between the toner supply member and the opposite surface of the toner carrier. The developing device according to 1.   4. The toner according to claim 1, wherein when the developer spikes and contacts the toner carrier, the toner is interposed between the carrier and the toner carrier. 5. Development device.   5. The developing device according to claim 1, wherein a distance between the toner carrier and the toner supply member is 5 to 20 times an average particle diameter of magnetic particles. 6. The developing device includes a photosensitive member, and when the non-image portion potential of the photosensitive member is VD, the exposed portion potential is VL, and the developing bias voltage is VB,
0 <| VD | − | VB | <| VD−VL | <250V
The developing device according to claim 1, wherein: One or more devices selected from a charging device for uniformly charging the surface of the latent image carrier and a cleaning device for the surface of the latent image carrier;
The latent image carrier;
An image forming process unit comprising a developing device that develops a latent image on the latent image carrier as an integral structure that is detachable from the image forming device,
An image forming process unit using the developing device according to claim 1 as the developing device. An intermediate transfer member onto which the toner image on the latent image carrier is transferred;
A primary transfer device for transferring a toner image on the latent image carrier to the intermediate transfer member;
A secondary transfer device for transferring the toner image on the intermediate transfer member to a transfer material;
An image forming apparatus comprising the image forming process unit according to claim 7.

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