JP2010096839A - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device that improves the durability of the device, by forming a thin layer of developer on a developer carrier, without exerting a strong stress to developer. <P>SOLUTION: The developing device 40 includes: a developing roller 41, serving as a developer carrier, which holds toner T, serving as one-component developer, on a moving surface and supplies toner T to a latent image on a photoreceptor 10 serving as a latent image carrier, and thereby develops the latent image; and a toner container 42, which is a developer container storing toner T which is to be supplied to the surface of the developing roller 41. The developing device has an air pump 31, which is an air inlet means for introducing air to toner T in a toner container 42. Air is introduced through the air pump 31, and the bulk density of the toner T in the toner container 42 decreases. Consequently, the toner T with the decreased bulk density comes into contact with the developing roller 41, the contact toner T is carried by the developing roller 41 and is thereby supplied to the developing roller 41. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a one-component developing device provided in an image forming apparatus such as a printer, a facsimile machine, and a copying machine, and an image forming apparatus provided with the same.

Conventionally, a non-magnetic or magnetic one-component developer (hereinafter referred to as toner) is carried on a developer carrier (hereinafter referred to as a developing roller), and a latent image carrier (hereinafter referred to as a photoreceptor) and development. There is known a one-component developing device that develops toner by supplying toner on a developing roller to a latent image on a photosensitive member in a developing region facing the roller.
As such a one-component developing device, a developer supply means for supplying toner to the developing roller, a roller-shaped supply roller that contacts the developing roller, and development so as to regulate the layer thickness of the toner on the developing roller Some include a restricting member disposed to face the roller with a predetermined gap.
In the configuration in which the toner is supplied by the contact-type supply roller, a strong stress is applied to the toner when the toner is supplied to the developing roller, so that the toner formed from the resin is easily deteriorated. Further, since the toner is subjected to a strong stress even when passing through the gap between the regulating member and the developing roller, the toner is likely to deteriorate. Toner deterioration is specifically the embedding of additives such as silica and titanium oxide, which are called fluidized particles attached around the toner base, into the toner resin. It becomes easy to adhere to the developing roller and the regulating member. Furthermore, the frictional heat is also applied when stress is applied, so that the toner is dissolved, and so-called filming on the developing roller and toner fixing to the regulating member occur. If filming on the developing roller or toner sticking to the regulating member occurs, the toner carrying amount of the developing roller becomes unstable and causes an image defect. Therefore, it is necessary to replace the developing roller and the regulating member. For this reason, the configuration that gives a strong stress to the toner deteriorates the durability of the developing device.

Patent Document 1 discloses a developing device provided with a fluidizing roller that disturbs and fluidizes toner carried on the developing roller by rotating upstream of the regulating member in the surface movement direction of the developing roller. Are listed. In such a developing device, mechanical stress due to the regulating member can be reduced compared to a configuration in which the fluidizing roller does not include the fluidizing member by fluidizing the toner, but strong stress is applied to the toner by the regulating member. It is still the configuration that gives. Further, since the toner is supplied to the developing roller by the contact type supply roller, a strong stress is applied to the toner at the time of supply.
Patent Document 2 describes a developing device that includes a non-contact supply roller and supplies charged toner by a potential difference between the supply roller and the development roller. In such a developing device, it is possible to prevent a strong stress from being applied to the toner during supply. However, since the layer thickness of the toner supplied to the developing roller is regulated by the regulating member, a strong stress is applied to the toner by the regulating member.
Japanese Patent Laying-Open No. 2005-91959 JP 2003-84565 A

If the toner carrying amount on the developing roller is not uniform in the developing region, the amount of toner supplied to the latent image on the photoreceptor becomes unstable, and a desired image density cannot be obtained. For this reason, the toner needs to be uniformly thinned and carried on the developing roller. Conventionally, the configuration for supplying toner onto the developing roller differs depending on whether the toner is magnetic or non-magnetic.
In a developing device using magnetic toner, the developing roller is composed of a developing sleeve whose surface moves and a magnet roller disposed inside the developing sleeve, and the magnetic roller attracts the magnetic toner by magnetic force to supply the toner onto the developing sleeve. To do. On the other hand, a developing device that uses non-magnetic toner has a configuration in which a predetermined voltage is applied to the developing roller and a polarity that precharges the toner to a predetermined polarity. The developing device uses a potential difference between the supply roller and the developing roller on the developing roller. The toner is moved, and the toner is supplied onto the developing roller.
As described above, as a configuration for supplying toner to the developing roller, a configuration using magnetic force and a configuration using potential difference are known. In any configuration, it is possible to carry the amount of toner necessary for development in the development area, but supply the toner so that the amount of toner carried is appropriate when the toner is supplied to the developing roller. It was difficult to control the amount. For this reason, in the conventional developing device, more toner than the amount necessary for development is carried on the developing roller, and the toner is uniformly thinned and carried on the developing roller by being regulated by the regulating member. Therefore, the conventional developing device needs a configuration in which the toner layer thickness on the developing roller is regulated by the regulating member.
However, as described above, the conventional developing device has a configuration in which the toner is strongly stressed by the restriction member, and this configuration deteriorates the durability of the developing device.

  The present invention has been made in view of the above problems, and its object is to form a thin layer of a developer on a developer carrying member without giving a strong stress to the developer, thereby improving the durability of the apparatus. It is an object of the present invention to provide a developing device capable of achieving the above and an image forming apparatus provided with such a developing device.

To achieve the above object, the invention according to claim 1 is a development in which a one-component developer is carried on a surface moving surface, and the developer is supplied to the latent image on the latent image carrier to develop the latent image. In a developing device having a developer carrying member and a developer container containing a developer to be supplied to the surface of the developer carrying member, the developing device includes gas introducing means for introducing gas into the developer in the developer container, When the gas introduction means introduces the gas, the bulk density of the developer is lowered, the developer having the lowered bulk density is brought into contact with the developer carrier, and the contacted developer is carried on the developer carrier. Thus, the developer is supplied to the developer carrying member.
According to a second aspect of the present invention, in the developing device of the first aspect, when the gas introduction means does not introduce gas, the bulk of the developer in the developer container does not reach the developer carrier. In the state where the gas introduction means introduces the gas, the bulk density of the developer is decreased, and the bulk of the developer in the developer container is increased, and the position of the upper portion is increased. It is characterized in that it becomes bulky enough to reach the developer carrying member.
The invention of claim 3 is the developing apparatus according to claim 1 or 2, further comprising a porous body disposed below the developer container and having a plurality of holes communicating in the vertical direction, and the gas introducing means. Is characterized in that gas is introduced from below the developer in the developing container through the porous body by sending gas from below the porous body.
According to a fourth aspect of the present invention, in the developing device of the third aspect, the opening diameters of the plurality of holes of the porous body are smaller than the average particle diameter of the developer.
According to a fifth aspect of the present invention, in the developing device of the third or fourth aspect, the porous body is formed of a porous sintered body.
According to a sixth aspect of the present invention, in the developing device according to the third or fourth aspect, the porous body is formed of a metal sintered body.
The invention according to claim 7 is the developing device according to claim 1, 2, 3, 4, 5 or 6, wherein the developer is supplied to the position where the developer is supplied from the developer container to the developer carrier. The developer carrying member on the downstream side in the surface movement direction of the developer carrier and on the upstream side in the surface movement direction of the developer carrier with respect to the developing region where the developer carrying member and the latent image carrier are opposed to each other. It is provided with developer charging means that is disposed in non-contact with the body and imparts electric charge to the developer on the developer carrying member.
In the invention of claim 8, the developing means develops the latent image on the latent image carrier by attaching a one-component developer, and the resulting toner image is finally transferred to a recording medium. In the image forming apparatus for forming an image, the developing device according to claim 1, 2, 3, 4, 5, 6 or 7 is used as the developing means.

As in the developing device having the configuration of claim 1, the inventors have reduced the bulk density of the developer by introducing gas into the developer in the developer container, and the developer having a reduced bulk density. It was experimentally confirmed that a uniform thin layer equivalent to one developer can be formed on the developer carrier when brought into contact with the developer carrier that moves on the surface.
This is thought to be due to the following reasons.
That is, by introducing a gas into the developer to reduce the bulk density of the developer, the cohesive force between the particles of the developer is lower than before the gas is introduced. The van der Waals works between the developer carrier and the developer particles in contact with the developer carrier when the surface of the developer carrier is in contact with the developer in a state where the cohesive force between the particles is reduced in this way. The force is greater than the cohesive force acting between the developer particles. As a result, the developer particles attracted by the van der Waals force are carried on the developer carrying member. Further, the force that the developer carrying member attracts the developer by the van der Waals force is not so large, and the developer particles carried on the developer carrying member are further carried on the developer particles. There is no power. For this reason, since the developer particles are not further adhered from the state in which a thin layer for one developer is formed on the developer carrier, a uniform thin layer for one developer is supported on the developer. It can be formed on the body.

Since a uniform thin layer equivalent to one developer can be formed on the developer carrier when the developer is supplied to the developer carrier, the layer thickness of the developer on the developer carrier can be reduced by the regulating member. The structure to regulate becomes unnecessary. Therefore, a thin layer of the developer can be formed on the developer carrying member without applying a strong stress to the developer by the regulating member as in the conventional developing device.
In addition, since the developer having a reduced bulk density is brought into contact with the developer carrying member to supply the developer to the developer carrying member, it is not necessary to provide a contact-type supply roller that stresses the developer during supply. It is possible to prevent a strong stress from being applied to the developer during supply.
In this way, it is not necessary to give a strong stress to the developer in order to supply the developer to the developer carrying member or to form a thin layer of the developer, thus preventing deterioration of the developer. The life of the developing device due to the deterioration of the developer can be extended. For this reason, it is possible to improve the durability of the developing device.

  According to the first to eighth aspects of the present invention, it is possible to improve the durability of the developing device by forming a thin layer of the developer on the developer carrying member without giving a strong stress to the developer. There is an effect.

Hereinafter, an embodiment in which the present invention is applied to an electrophotographic printer (hereinafter simply referred to as a printer 100) as an image forming apparatus will be described.
FIG. 2 is a schematic configuration diagram of the printer 100 according to the embodiment.
The printer 100 includes a photosensitive member 10 that is a drum-shaped latent image carrier having a photosensitive layer formed on a substrate. Around the photosensitive member 10, a developing device 40, a charging device 20, a static elimination lamp 51, and a cleaning device 50 are provided. And a transfer roller 70 and the like. Further, the printer 100 is sensitive to the position where the photoconductor 10 faces the developing roller 41 provided in the developing device 40 on the upstream side in the moving direction of the photoconductor surface and the position where the photoconductor 10 faces the charging device 20. An exposure apparatus (not shown) that irradiates a laser beam 30 corresponding to image information at a position downstream of the body surface movement direction is provided. Further, a transfer conveyance belt 71 that conveys transfer paper P as a recording medium at a transfer position where the photoconductor 10 and the transfer roller 70 face each other, a paper feed cassette 60 that accommodates the transfer paper P, And a paper feed roller 61 that feeds the uppermost sheet of the transfer paper P toward the transfer position. Further, a pair of registration rollers 62 that conveys the transfer paper P delivered by the paper supply roller 61 toward the transfer position at a predetermined timing, and a transfer paper on which the toner image is transferred at the transfer position and carries an unfixed toner image. And a fixing device 80 for fixing the toner image to P. The transfer roller 70 is disposed at a position facing the photoconductor 10 with the transfer conveyance belt 71 interposed therebetween, and a voltage is applied by a transfer power source (not shown) to form a transfer electric field between the transfer roller 70 and the photoconductor 10.

Next, the operation of the printer 100 will be described.
The photoconductor 10 is rotationally driven in a direction indicated by an arrow in FIG. 2 by a driving device (not shown). The photoconductor 10 is uniformly charged by the charging device 20, and an electrostatic latent image is formed on the surface of the photoconductor 10 by writing with laser light 30 corresponding to image information from an exposure device (not shown).
The electrostatic latent image on the surface of the photoreceptor 10 is visualized by the toner attached thereto by the developing device 40 according to the present invention. On the other hand, the transfer paper P taken out from the paper feed cassette 60 by the paper feed roller 61 and stopped is temporarily stopped while being sandwiched between the two rollers of the registration roller pair 62. Then, the registration roller pair 62 is driven so that the toner image formed on the photoreceptor 10 and the transfer paper P overlap at the transfer position, and the transfer transferred from the registration roller pair 62 to the transfer conveyance belt 71 is performed. The paper P reaches the transfer position where the photoconductor 10 and the transfer roller 70 face each other. At the transfer position, the toner image on the photoconductor 10 is transferred onto the transfer paper P by a transfer electric field formed between the photoconductor 10 and the transfer roller 70.
The transfer paper P onto which the toner image has been transferred is separated from the surface of the photoreceptor 10 by being carried and conveyed by the transfer conveyance belt 71 and conveyed to the fixing device 80 by the transfer conveyance belt 71. The transfer paper P that has reached the fixing device 80 is fixed to a toner image by heat and pressure at a fixing nip formed by two rollers provided in the fixing device 80, and is transferred to a discharge tray (not shown) outside the printer 100. Is ejected.
On the other hand, the toner remaining on the surface of the photoreceptor 10 after passing the transfer position facing the transfer roller 70 is removed by the cleaning device 50, and the charge remaining on the surface of the photoreceptor 10 is erased by the charge eliminating lamp 51. Is done.

  As the charging device 20 for uniformly charging the surface of the photoconductor 10, a scorotron charger or a corotron charger can be used. A non-contact charging roller or a contact type charging roller can also be used.

Next, the developing device 40 that is a characteristic part of the printer 100 will be described.
FIG. 1 is an enlarged explanatory view of a photoconductor unit including the developing device 40 of this embodiment.
As shown in FIG. 1, the developing device 40 includes a toner container 42 that contains toner T, which is a non-magnetic one-component developer, and the toner T is supplied from the toner container 42 and carries the toner T to carry the photoreceptor 10. A developing roller 41 that conveys the toner to a developing region that is opposite to the toner container 42, and an air pump 31 that introduces air into the toner container 42. An air chamber 45 into which air is sent from the air pump 31 is disposed below the toner container 42, and a porous body made of a porous sintered body and having a plurality of holes between the air chamber 45 and the toner container 42. 46 is arranged. The toner container 42 is connected to a toner hopper 44 that contains toner T to be supplied to the toner container 42. The toner hopper 44 is replenished with toner T from a toner bottle (not shown) by a toner supply device (not shown). A container agitator 47 and a hopper agitator 48 are disposed in the toner container 42 and the toner hopper 44, respectively. The toner T in the toner container 42 and the toner hopper 44 is agitated to maintain fluidity.

  The developing roller 41 moves on the surface in the clockwise direction in FIG. 1 as indicated by an arrow in FIG. The surface of the developing roller 41 with respect to the developing region where the developing roller 41 is opposed to the photoreceptor 10 on the downstream side in the surface movement direction of the developing roller 41 with respect to the position where the toner T is supplied from the toner container 42. A toner charging device 43 that applies charge to the toner is disposed at a position facing the surface of the developing roller 41 on the upstream side in the movement direction. The toner charging device 43 disposed in the developing device 40 is a non-contact charging device, and a scorotron charger or a corotron charger can be used. In addition, a charging roller can be used as long as it is non-contact.

  The air pump 31 is connected to an intake pipe 32 connected to the air chamber 45. When the air pump 31 is driven, air is introduced into the air chamber 45 through the intake pipe 32. Further, an exhaust pipe 33 is connected to the upper portion of the toner container 42 so that air in the toner container 42 can be exhausted.

When the developing device 40 is stopped, the air pump 31 is also stopped, and the position above the bulk of the toner T in the toner container 42 below the developing roller 41 is the position A in FIG. . When the developing device 40 starts the developing operation, the air pump 31 is also driven, and air is supplied into the toner container 42 through the porous body 46 installed below the toner container 42. As a result, air spreads throughout the toner T in the toner container 42, the bulk density of the toner T decreases, the position of the upper part of the bulk of the toner T rises to the position B in FIG. 1, and the toner T is developed. Contact the roller 41. The toner T that has come into contact with the developing roller 41 is pumped up by the developing roller 41.
As the toner T approaches the developing roller 41, van der Waals force acts between the toner T particles (hereinafter referred to as toner particles) and the developing roller 41, and the toner particles are attracted to the developing roller 41. On the other hand, the adhesion force (cohesion force) between the toner particles, which is the force in the direction of peeling off the toner particles attached to the developing roller 41 from the developing roller 41, is small because sufficient air is introduced into the toner T. It has become. For this reason, since the adhesion force between the developing roller 41 and the toner particles acts larger than the cohesion force between the toner particles, the toner can be adhered to the developing roller 41 substantially more substantially.

As described above, when the image signal is input to the developing device 40, the air pump 31 is driven to reduce the bulk density of the toner T in the toner container 42 and raise the position of the upper portion of the bulk of the toner T. . As a result, the position of the upper part of the bulk of the toner T becomes higher during the developing operation than when the developing device 40 is stopped, and the toner T in the toner container 42 comes into contact with the developing roller 41 during the developing operation. Since the toner adheres to the roller 41 in an amount equivalent to one layer, the toner T can be uniformly thinned and carried on the developing roller 41. For this reason, there is no need for a regulating member for regulating the toner carrying amount on the developer carrying member as in the conventional developing device.
Therefore, a thin layer of the developer can be formed on the developer carrying member without applying a strong stress to the developer by the regulating member as in the conventional developing device. In addition, the regulation of the toner layer thickness by the regulating member repeatedly applies a large force to the developing roller, which increases the load on the developing roller and each member that supports the developing roller, and this load also reduces the life of the developing device. However, in the developing device 40 that does not include a regulating member, such a decrease in life can also be prevented.

Further, when the toner T in the toner container 42 and the developing roller 41 come into contact with each other, the toner T carried on the developing roller 41 reaches a portion facing the toner charging device 43 by the surface movement of the developing roller 41, and the toner charging device. 43 deviates a predetermined amount of charge. The toner T that has passed through the portion facing the toner charging device 43 reaches the development region. In the developing area, the toner T charged in accordance with the image potential of the latent image on the photoconductor 10 moves from the developing roller 41 to the photoconductor 10 to form a toner image.
In the printer 100, as a developing method for forming a toner image on the photoreceptor 10, a one-component developing method used for a contact or non-contact developing method is used. Various known methods can be used as the contact or non-contact development method. For example, a contact development method using an aluminum sleeve as a developer carrier, a contact development method using a conductive rubber belt as a developer carrier, and a conductive resin layer containing carbon black, metal filler, etc. on the surface of an aluminum base tube. There is a non-contact development method using the formed developer carrier.
The toner T supplied to the latent image on the photoreceptor 10 forms a toner image, is transferred to the transfer paper P at the transfer position, and is fixed to the transfer paper P by the fixing device 80. On the other hand, the toner T that is not used for development in the development region and remains on the development roller 41 reaches the supply position where the development roller 41 contacts the toner T in the toner container 42 while being carried on the surface of the development roller 41. The toner T that has come into contact with the supply position adheres to the portion where the toner T has been consumed in the developing region on the surface of the developing roller 41. On the other hand, the portion where the toner T is consumed in the development region passes through the supply position while the toner T that has passed through the development region remains attached. As a result, the toner T is supplied only to the portion where the toner T is consumed, a uniform thin layer of the toner T is formed again on the developing roller 41, and the toner T newly supplied at the supply position by the toner charging device 43. Is charged.

The developing device 40 of the present embodiment does not include a collecting member that collects the toner remaining on the surface of the developing roller 41 that has passed through the developing area, and the toner T that has passed through the developing area is used until the developing roller 41 is used for development. It remains in the state of adhering to. In the conventional developing device, the toner on the developing roller is rubbed by the regulating member. Therefore, if the toner is held on the developing roller, the toner held on the developing roller may be significantly deteriorated as compared with other toners. And a recovery member that recovers the toner that has passed through the development area. On the other hand, in the case of the developing device 40 according to the present embodiment, since the toner is not easily deteriorated by passing through the restricting portion by the restricting member as in the conventional developing device, there is toner remaining on the developing roller 41. However, it is difficult to cause problems. For this reason, it is not necessary to arrange a collection member, the number of members can be reduced, and the cost can be reduced.
The developing device 40 according to the present embodiment is configured not to include the recovery member as described above. However, the developing device including the characteristic portion of the present invention may be configured to include the recovery member.

The bulk density of the toner T in the toner container 42 is 0.5 to 0.7 [g / cc] when the air pump 31 is stopped, but the air pump 31 starts to be driven and air is introduced. Then, it becomes 0.35 to 0.45 [g / cc]. If the flow rate of air is 0.4 [Nl / min] or more per unit area, the volume of the toner T can be sufficiently increased, and the toner can be adhered to the developer carrying member. FIG. 3 shows the relationship between the inflow amount of air introduced into the toner T in the toner container 42 and the increase amount of the bulk of the toner T. The porous body 46 at this time is a porous sintered body of ultra-high density polyethylene described later.
Further, since the opening diameters of the plurality of holes provided in the porous body 46 are smaller than the average particle diameter of the toner T, the toner T is transferred from the toner container 42 above the porous body 46 to below the porous body 46. It can prevent falling into the air chamber 45.

In the developing device 40, a DC scorotron charger was used as the toner charging device 43, and a voltage of −5 [kV] was applied to the wire and −50 [V] was applied to the grid to give a charge to the toner.
The toner T has a weight average particle diameter of 5.8 [μm], and when the toner T adhesion amount on the surface of the developing roller 41 is 0.3 [mg / cm ² ], the charge amount of the toner T is −38 [ μC / g].

FIG. 4 is a schematic explanatory diagram of the air pump 31 provided in the developing device 40.
The air pump 31 of this embodiment is a diaphragm air pump. The air pump 31 includes a pump main body 310, a vibration plate 311 that vibrates with respect to the pump main body 310, and a rotor 312 that vibrates the vibration plate 311 by being rotationally driven. The pump main body 310 includes an intake valve 313 that is urged toward the inner wall of the pump main body 310 so as to block an upper opening of the pump main body 310 in the figure by an urging member (not shown), and an urging member (not shown). And an exhaust valve 314 urged toward the outer wall of the pump body 310 so as to close the lower opening of the pump body 310 in the figure. In the air pump 31, the diaphragm 311 vibrates as indicated by an arrow D when the rotor 312 rotates in the direction of arrow C in the drawing. When the diaphragm 311 moves to the right side in FIG. 4, the intake valve 313 moves to the inside of the pump body 310 to release the upper opening in the drawing, and intake is performed as indicated by an arrow A1 in the drawing. On the other hand, when the diaphragm 311 moves to the left side in FIG. 4, the intake valve 313 closes the upper opening in the figure by the urging force of the urging member, and the exhaust valve 314 moves outward with respect to the pump body 310. Then, the lower opening in the figure is released, and exhaust is performed as indicated by arrow A2 in the figure.

The lower opening in the figure of the pump body 310 provided with the exhaust valve 314 is connected to the air chamber 45 of the developing device 40 via the intake pipe 32, and the air pump 31 is driven so that the toner is discharged from the air pump 31 to the toner. Air is introduced into the container 42.
As in the developing device 40, by providing the air chamber 45 below the porous body 46, pulsation is eliminated, air is uniformly distributed to the toner T in the toner container 42, and the bulk density of the toner T becomes uniform. The toner T can be uniformly adhered to the developing roller 41. Further, the pressure in the toner container 42 may increase due to the introduction of air, and the toner may be scattered. For this reason, as shown in FIG. 5, in addition to the intake air pump 31a connected to the intake pipe 32 of the developing device 40 and introducing air into the toner T, it is connected to the exhaust pipe 33 of the developing device 40. It is desirable to connect an exhaust air pump 31b for venting to reduce the pressure. In the configuration shown in FIG. 5, when the intake air pump 31a is driven, the airflow indicated by A2 exhausted from the intake air pump 31a is introduced into the developing device 40 as indicated by A3. On the other hand, when the exhaust air pump 31b is driven, an airflow is drawn to the exhaust air pump 31b as indicated by A5, and an airflow exhausted from the developing device 40 is generated as indicated by A4. The air can be vented to reduce the pressure. The gas sucked by the exhaust air pump 31b is discharged out of the apparatus from the exhaust air pump 31b as indicated by A6.
As the air pump 31, a diaphragm type air pump can be used as in this embodiment, and a screw pump and a blower pump can be used, but a diaphragm type that can be easily reduced in size and weight. An air pump is desirable.
In this embodiment, air is introduced as a gas to be introduced into the toner container 42 by the air pump 31. However, the air is not limited to air and is inactive with respect to the toner T, and is introduced into the toner container 42. Any gas that can reduce the bulk density of T may be used.

Next, a developer carrier that can be used in the developing device 40 to which the present invention is applied will be described.
Examples of the surface layer coating material for the developer carrying member include materials containing a resin such as silicon, acrylic, and polyurethane, and rubber. Another example of the material is 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. Further, as general resin materials that can be used for the surface layer coating material of the developer carrier, polytetrafluoroethylene (PTFE), tetrafluoroethylene perfluoroalkyl vinyl ether (PFA), tetrafluoroethylene / hexafluoropropylene heavy Polymer (FEP), polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene / ethylene copolymer (ETFE), chlorotrifluoroethylene / ethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF). In order to obtain conductivity, a conductive material such as carbon black is often contained in this. It is also possible to reduce the resistance by mixing conductive polymer resins such as doped polyacetylene and polythiophene. In order to coat the toner carrier more uniformly, another resin may be mixed. Regarding the electrical resistance, the bulk resistivity including the coat layer is set, and the resistance and adjustment of the base layer are performed so that it can be set to 10 ³ to 10 ⁸ [Ω · cm]. Since the volume resistivity of the base layer used in this embodiment is 10 ³ to 10 ⁵ [Ω · cm], the volume resistivity of the surface layer may be set slightly higher.

In the developing device and the image forming apparatus, since a rigid drum-shaped photosensitive member based on an aluminum tube is used, the toner carrier is an elastic rubber material developer carrier, and the hardness is good. The range of 10-70 [°] (JIS-A) is good. The toner carrier preferably has a diameter of 10 to 30 [mm]. In the present embodiment, one having a diameter of 16 [mm] is used. Further, the surface of the toner carrier was appropriately changed to have a roughness Rz (10-point average roughness) of 0.1 to 4 [μm]. Here, silicon, butadiene, NBR, hydrin, EPDM, urethane rubber or the like can be used as a rubber material for the developing roller.
Further, an endless belt using a thin metal plate can be used as a toner carrier for contact development in order to lower the hardness.

Next, the sintered porous body used in the porous body 46 will be described.
The sintered porous body made of resin contains particles such as low density polyethylene, high density polyethylene, ultra high density polyethylene, polypropylene, polymethyl methacrylate (PMMA), tetrafluoroethylene, polystyrene, polyetheretherketone (PEEK), etc. Sintered into the mold and produced.
Since some resins react with the toner, polyolefin resins such as polyethylene, fluorine resins, materials such as PET and PEEK are better. In this embodiment, a porous sintered body having an opening diameter of 4 [μm] obtained by sintering a resin having a particle size of 10 [μm] made of ultra-high density polyethylene is used, but other resins may be used.
The resin sintered body can be molded and can be produced at low cost.
In addition, as the porous body 46, not only a resin thing but a metal sintered metal body may be sufficient. As the metal sintered body, a porous sintered body obtained by sintering particles such as AL, copper, steel, stainless steel (SUS316, SUS304, SUS430, etc.), bronze, and brass can be used.

  Further, it is preferable that the toner T used in the developing device 40 of this embodiment has an average particle diameter of 3 to 8 [μm] in order to realize a high quality image. In this embodiment, the toner T has a weight average particle diameter of 4 to 7 [μm], more preferably 4 to 6 [μm]. If the weight average particle diameter is less than 4 [μm], problems such as contamination in the machine due to toner scattering during long-term use, image density reduction in a low-humidity environment, and poor photoreceptor cleaning are likely to occur. Further, when the weight average particle diameter exceeds 8 [μm], the resolution of minute spots of 100 [μm] or less is not sufficient, and the image quality tends to be inferior due to many scattering to non-image portions.

The toner is mainly formed of a resin component, a pigment component, a wax component, and an external additive.
As resins, polystyrene resin, epoxy resin, polyester resin, polyamide resin, styrene acrylic resin, styrene methacrylate resin, polyurethane resin, vinyl resin, polyolefin resin, styrene butadiene resin, phenol resin, polyethylene resin, silicon resin, butyral resin, terpene There are resins, polyol resins and the like. Examples of vinyl resins include styrene such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene, and homopolymers thereof: styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer. Polymer, styrene-vinyl naphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methacrylic copolymer Acid methyl copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer Coalescence, styrene-vinyl ethyl acetate Copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester Styrene copolymers such as copolymers: polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate and the like.

The polyester resin is composed of a dihydric alcohol as shown in the following group A and a dibasic acid salt as shown in the group B, and further a trihydric or higher alcohol as shown in the group C or Carboxylic acid may be added as a third component.
Group A: ethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4 butanediol, neopentyl glycol, 1,4 butenediol, 1,4-bis (hydroxymethyl) cyclohexane Bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylene (2,2) -2,2′-bis (4-hydroxyphenyl) propane, polyoxypropylene (3,3) -2, 2-bis (4-hydroxyphenyl) propane, polyoxyethylene (2,0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (2,0) -2,2′-bis (4 -Hydroxyphenyl) propane and the like.
Group B: maleic acid, fumaric acid, mesaconic acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, malonic acid, linolenic acid, or These acid anhydrides or esters of lower alcohols.
Group C: Trivalent or higher alcohols such as glycerin, trimethylolpropane and pentaerythritol, and trivalent or higher carboxylic acids such as trimellitic acid and pyromellitic acid.
As the polyol resin, an alkylene oxide adduct of an epoxy resin and a dihydric phenol, or a compound having one active hydrogen in the molecule that reacts with the glycidyl ether and the epoxy group, and an active hydrogen that reacts with the epoxy resin in the molecule. There are those obtained by reacting two or more compounds.

The following are used as the pigment used in the present invention.
Examples of black pigments include azine dyes such as carbon black, oil furnace black, channel black, lamp black, acetylene black, and aniline black, metal salt azo dyes, metal oxides, and composite metal oxides.
Examples of yellow pigments include cadmium yellow, mineral fast yellow, nickel yellow, navel yellow, naphthol yellow S, hansa yellow G, hansa yellow 10G, benzidine yellow GR, quinoline yellow lake, permanent yellow NCG, and tartrazine lake. .
Examples of the orange pigment include molybdenum orange, permanent orange GTR, pyrazolone orange, Vulcan orange, indanthrene brilliant orange RK, benzidine orange G, and indanthrene brilliant orange GK.
Examples of red pigments include Bengala, Cadmium Red, Permanent Red 4R, Resol Red, Pyrazolone Red, Watching Red Calcium Salt, Lake Red D, Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B.
Examples of purple pigments include fast violet B and methyl violet lake.
Examples of blue pigments include cobalt blue, alkali blue, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated, fast sky blue, and indanthrene blue BC.
Examples of green pigments include chrome green, chromium oxide, pigment green B, and malachite green lake.
These can use 1 type (s) or 2 or more types. Especially for color toners, uniform dispersion of good pigments is essential. Instead of putting pigments directly into a large amount of resin, a master batch in which pigments are once dispersed at a high concentration is prepared and diluted. The method of throwing in is used. In this case, a solvent is generally used to assist dispersibility. However, there is a problem of environment and the like, and in the present invention, water is used for dispersion. When water is used, temperature control is important so that residual moisture in the masterbatch does not become a problem.

  In the toner of the present invention, a charge control agent is blended (internally added) inside the toner particles. The charge control agent makes it possible to control the optimum charge amount according to the development system. In particular, in the developing device to which the present invention is applied, the balance between the particle size distribution and the charge amount can be further stabilized. For controlling the toner to be positively charged, nigrosine and quaternary ammonium salts, triphenylmethane dyes, imidazole metal complexes and salts can be used alone or in combination of two or more. Further, salicylic acid metal complexes, salts, organic boron salts, calixarene compounds, and the like are used for controlling the toner to be negatively charged. Further, a release agent can be internally added to the toner in the present invention to prevent offset at the time of fixing. Release agents include natural waxes such as candelilla wax, carnauba wax and rice wax, montan wax and derivatives thereof, paraffin wax and derivatives thereof, polyolefin wax and derivatives thereof, sazol wax, low molecular weight polyethylene, and low molecular weight polypropylene. And alkyl phosphate esters. The melting point of these release agents is preferably 65 to 90 [° C.]. If it is lower than this range, blocking during storage of the toner tends to occur, and if it is higher than this range, offset tends to occur in a region where the fixing temperature is low.

Additives may be added for the purpose of improving the dispersibility of a release agent or the like. Additives include styrene acrylic resin, polyethylene resin, polystyrene resin, epoxy resin, polyester resin, polyamide resin, styrene methacrylate resin, polyurethane resin, vinyl resin, polyolefin resin, styrene butadiene resin, phenol resin, butyral resin, terpene resin, There is a polyol resin or the like, and a mixture of two or more of these resins may be used.
As the resin, crystalline polyester may be used. It is an aliphatic polyester having crystallinity, having a sharp molecular weight distribution, and increasing the absolute amount of its low molecular weight as much as possible. This resin undergoes a crystal transition at the glass transition temperature (Tg), and at the same time, the melt viscosity suddenly decreases from the solid state and exhibits a fixing function to paper. By using this crystalline polyester resin, low-temperature fixing can be achieved without excessively reducing the Tg and molecular weight of the resin. Therefore, there is no decrease in storage stability associated with a decrease in Tg. Further, there is no excessively high gloss and offset resistance deterioration due to the low molecular weight. Therefore, the introduction of the crystalline polyester resin is very effective for improving the low-temperature fixability of the toner.
As the toner T, an inorganic fine powder may be adhered or fixed to the toner surface as a fluidity improver. The average particle size of the inorganic fine powder is suitably 10 to 200 [nm]. When the particle size is smaller than 10 [nm], it is difficult to create an uneven surface having an effect on fluidity, and when the particle size is larger than 200 [nm], the powder shape becomes rough, which is a problem of toner shape. Occurs.
As the inorganic fine powder of the present invention, Si, Ti, Al, Mg, Ca, Sr, Ba, In, Ga, Ni, Mn, W, Fe, Co, Zn, Cr, Mo, Cu, Ag, V, Zr, etc. Oxides, hydroxides, carbonates, sulfides, and composite oxides. Of these, the following oxides are often used from the viewpoint of safety and stability.
In particular, fine particles of silicon oxide (silica), titanium oxide, and aluminum oxide (alumina, corundum) are preferably used.

Furthermore, it is effective to perform a surface modification treatment of the additive with a hydrophobizing agent or the like. A typical example of the hydrophobizing agent is a silane coupling agent, which includes the following.
Dimethyldichlorosilane, trimethylchlorosilane, methyltrichlorosilane, allyldimethyldichlorosilane, allylphenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, p-chloroethyltrichlorosilane, Chloromethyldimethylchlorosilane, chloromethyltrichlorosilane, hexaphenyldisilazane, hexatolyldisilazane, etc.
The inorganic fine powder is preferably used in an amount of 0.1 to 2% by weight based on the toner. If it is less than 0.1 [wt%], the effect of improving toner aggregation is poor, and if it exceeds 2 [wt%], there are problems such as toner scattering between fine wires, contamination in the machine, scratches and abrasion of the photoreceptor. It tends to occur.
In addition, a charge control agent may be attached or fixed to the surface of at least a powder composed of a resin and a pigment so that the powder surface shape has a small period and a large period. The average particle size is optimally as small as 5 to 200 [nm].
Further, the toner of the present invention may further contain other additives within a range that does not substantially adversely affect, for example, metal soap powder such as Teflon powder and zinc stearate powder, lubricant powder such as polyvinylidene fluoride powder, or oxidation powder. Abrasives such as cerium powder, silicon carbide powder, strontium titanate powder, or powder obtained by coating the conductive particles on, for example, carbon black powder, zinc oxide powder, tin oxide powder, indium oxide powder, and insulating powder A small amount of a conductivity-imparting agent such as a body can be used as a developability improver.

Note that the printer 100 according to the present embodiment is a monochrome image forming apparatus in which only one photosensitive unit is disposed with respect to the transfer conveyance belt 71. However, as shown in FIG. The present invention is applicable even to a color image forming apparatus on which the photosensitive unit is mounted.
The printer 100 shown in FIGS. 2 and 6 has a configuration in which the toner image on the photoconductor 10 is directly transferred to the transfer paper P. However, the toner on the photoconductor is transferred to the transfer paper via the intermediate transfer body. It may be a configuration.

As described above, according to the present embodiment, the toner T, which is a one-component developer, is carried on the surface that moves, and the toner T is supplied to the latent image on the photoconductor 10 that is a latent image carrier to form a latent image. In a developing device 40 having a developing roller 41 that is a developer carrying member to be developed and a toner container 42 that is a developer container that contains toner T to be supplied to the surface of the developing roller 41, the toner T in the toner container 42 An air pump 31 that is a gas introduction unit that introduces air is provided. When air is introduced by the air pump 31, the bulk density of the toner T in the toner container 42 is lowered, and the toner T with the lowered bulk density is transferred to the developing roller 41. The toner T is supplied to the developing roller 41 by being carried on the developing roller 41. By introducing air into the toner T and reducing the bulk density of the toner T, the cohesive force between the particles of the toner T is lowered than before the air is introduced. Thus, when the surface of the developing roller 41 comes into contact with the toner T in a state where the cohesive force between the particles is reduced, the van der Waals force acting between the developing roller 41 and the developer particles in contact with the surface of the developing roller 41. This is larger than the cohesive force acting between the particles of the toner T. As a result, the toner T particles attracted by van der Waals force are carried on the developing roller 41. Further, the force that the developing roller 41 attracts the toner T due to the van der Waals force is not so large, and a force enough to carry other toner particles on the toner T particles carried on the developing roller 41 is generated. Absent. For this reason, since the particles of the other toner T are not further adhered from the state where the thin layer of the toner T is formed on the developing roller 41, the uniform thin layer of the toner T is formed on the developing roller. 41 can be formed.
When the toner T is supplied to the developing roller 41, a uniform thin layer corresponding to one layer of the toner T can be formed on the developing roller 41. Therefore, the layer thickness of the developer on the developer carrier is regulated by the regulating member. The structure to perform becomes unnecessary. Therefore, a thin layer of the toner T can be formed on the developing roller 41 without applying a strong stress to the developer by the regulating member as in the conventional developing device.
Further, since the toner T having a reduced bulk density is brought into contact with the developing roller 41 to supply the toner T to the developing roller 41, it is not necessary to provide a contact-type supply roller that stresses the toner T during supply. Sometimes, it is possible to prevent the toner T from being subjected to strong stress.
Thus, since it is not necessary to apply a strong stress to the toner T in order to supply the toner T to the developing roller 41 or to form a thin layer of the toner T, the deterioration of the toner T is prevented. The life of the developing device 40 due to the deterioration of the toner T can be extended. For this reason, the durability of the developing device 40 can be improved.

  Further, in the developing device 40, when air is not introduced by the air pump 31, the bulk of the toner T is at a position A where the upper portion does not reach the developing roller 41, and the bulk density of the toner T is introduced by introducing air by the air pump 31. Decreases, the position of the upper portion of the toner T rises to a position B that reaches the developing roller 41. By reducing the bulk density of the toner T, the position of the upper portion of the toner T can be raised, and the fluidity is further improved, so that a uniform toner thin layer can be formed on the developing roller 41.

  Further, the developing device 40 includes a porous body 46 that is disposed below the toner container 42 and has a plurality of holes communicating in the vertical direction, and the air pump 31 sends air from below the porous body 46. Then, air is introduced from below the toner T in the toner container 42 through the porous body 46. By introducing air from the lower side of the toner container 42 through the porous body 46, the toner T is dispersed and fluidized to lower the bulk density of the toner. As a result, the toner T can uniformly contact the developing roller 41, and the thin layer on the developing roller 41 by the toner T becomes uniform.

  In addition, since the opening diameters of the plurality of holes of the porous body 46 of the developing device 40 are smaller than the average particle diameter of the toner T, the toner T flows into and out of the air chamber 45, and the toner flows into the holes. Therefore, stable air can be supplied to the toner T in the toner container 42. Therefore, the position B above the bulk of the toner T when fluidized is stabilized.

Further, since the porous body 46 is formed of a porous sintered body, the material is inexpensive and light, and thus a compact and light developing device 40 can be obtained at low cost.
Further, the porous body 46 may be formed of a metal sintered body.

  Further, the developing device 40 is located downstream in the surface moving direction of the developing roller 41 with respect to the position where the toner T is supplied from the toner container 42 to the developing roller 41 and upstream in the surface moving direction of the developing roller 41 with respect to the developing region. A non-contact toner charging device 43 as a developer charging unit is provided at the side position. By charging the toner on the developing roller 41 with a non-contact charging device, it is possible to maintain a thin layer of the toner T that is supported by the van der Waals force and has a weak adhesion to the developing roller 41.

  Further, the developing unit develops the latent image on the photoreceptor 10 as a latent image carrier by attaching the toner T as a one-component developer, and the toner image thus obtained is finally recorded on a recording medium. In the printer 100 that is an image forming apparatus that transfers an image to a certain transfer paper P and forms an image, by using the developing device 40 of this embodiment as a developing unit, a highly durable developing device can be obtained. The image forming apparatus can reduce the maintenance frequency.

FIG. 3 is an enlarged explanatory diagram of a photoreceptor unit according to the embodiment. 1 is a schematic configuration diagram of a printer according to an embodiment. 6 is a graph showing a relationship between an inflow amount of air introduced into toner in a toner container and an increase amount of toner bulk. Schematic explanatory drawing of an air pump. Explanatory drawing of the developing apparatus provided with the exhaust air pump. FIG. 2 is a schematic configuration diagram of a printer including a plurality of photoconductor units.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Photoconductor 20 Charging device 30 Laser beam 31 Air pump 31a Intake air pump 31b Exhaust air pump 32 Intake pipe 33 Exhaust pipe 40 Developing device 41 Developing roller 42 Toner container 43 Toner charging device 44 Toner hopper 45 Air chamber 46 Porous body 47 Container Agitator 48 Hopper agitator 50 Cleaning device 51 Static elimination lamp 60 Paper feed cassette 61 Paper feed roller 62 Registration roller pair 70 Transfer roller 71 Transfer conveyance belt 80 Fixing device 100 Printer 310 Pump body 311 Diaphragm 312 Rotor 313 Intake valve 314 Exhaust valve P Transfer paper

Claims (8)

A developer carrying member for carrying a one-component developer on a surface that moves and supplying the developer to the latent image on the latent image carrying member to develop the latent image;
In a developing device having a developer container containing a developer to be supplied to the surface of the developer carrying member,
Gas introduction means for introducing gas into the developer in the developer container,
When the gas introduction means introduces a gas, the bulk density of the developer decreases,
The developer having a reduced bulk density is brought into contact with the developer carrier, and the developer is supplied to the developer carrier by the developer being brought into contact with the developer carrier. Development device. The developing device according to claim 1.
In the state where the gas introduction means does not introduce gas, the bulk of the developer in the developer container is a bulk where the upper part does not reach the developer carrier,
In the state where the gas introduction means introduces gas, the bulk density of the developer is lowered, so that the bulk of the developer in the developer container is increased and the position of the upper part is raised so that it reaches the developer carrier. A developing device characterized by having a bulk of The developing device according to claim 1 or 2,
A porous body having a plurality of holes arranged below the developer container and communicating in the vertical direction;
A developing apparatus, wherein the gas introduction means introduces gas from below the developer in the developer container through the porous body by sending gas from below the porous body. The developing device according to claim 3.
The developer supply apparatus according to claim 1, wherein an opening diameter of the plurality of pores of the porous body is smaller than an average particle diameter of the developer. The developing device according to claim 3 or 4,
A developing device, wherein the porous body is formed of a porous sintered body. The developing device according to claim 3 or 4,
A developing apparatus, wherein the porous body is formed of a metal sintered body. The developing device according to claim 1, 2, 3, 4, 5 or 6.
The developer carrier and the latent image carrier face each other on the downstream side of the surface of the developer carrier relative to the position where the developer is supplied from the developer container to the developer carrier. A developer charge that is disposed in a non-contact manner with respect to the developer carrier at a position upstream of the developer carrier in the surface movement direction of the developer carrier and imparts a charge to the developer on the developer carrier. A developing device comprising means. In an image forming apparatus that develops a latent image on a latent image carrier by attaching a one-component developer to the latent image carrier, and finally transfers the toner image thus obtained to a recording medium to form an image. ,
An image forming apparatus using the developing device according to claim 1, 2, 3, 4, 5, 6, or 7 as the developing means.

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