JPH10232551A - Developing device, electrifier and transfer device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact developing device, an electrifier and a transfer device, high in electrification efficiency and small in the generation of ozone. SOLUTION: This electrifier is provided with a first electrode 15a arranged in the proximity to a body to be electrified 12 and a second electrode 15b which is disposed in a position held between the first electrode 15a and the body to be electrified 12 with an insulating layer 15c between the second and first electrodes 15b and 15a and provided with a large number of openings 15d for regulating the ionizing region of an electric discharge generated in an electric field, to the gap between the second and first electrodes 15b and 15a. When voltages applied to the first and second electrode 15a and 15b are defined as Vdis and Vele respectively, the thickness of the insulating layer 15c is defined as Tins and the diameters of the openings 15d of the second electrode 15b are defined as Dele, a relation as an equation of 10<(ΔV/Tins) exp (-0.2Dele/ Tins), where ΔV=|Vdis-Vele| is satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a copying machine,
The present invention relates to a developing device, a charging device, and a transfer device used in an electrophotographic image forming apparatus such as a printer.

[0002]

2. Description of the Related Art Conventionally, a toner is attached to an electrostatic latent image formed on an image carrier, which is used in an electrophotographic image forming apparatus, to visualize the electrostatic latent image to form a developed image. As a developing device, a one-component developing method using a one-component developer containing only toner and a two-component developing method using a two-component developer composed of a toner and a carrier are known. These developing devices are provided with a rotatable developer carrier at a position facing the image carrier, and the developer is carried on the surface of the developer carrier and the developer carrier is rotated by the rotation of the developer carrier. The image carrier is transported to the developing areas facing each other. In the developing area, an electric field is formed by a developing bias voltage applied between the developer carrier and the image carrier, and the electric field causes the toner to transfer to an electrostatic latent image on the image carrier, thereby causing the image carrier to move. A developed image with toner is formed on the body.

In such a developing device, it is necessary to apply a predetermined amount of charge to the toner in order to surely transfer the toner to the electrostatic latent image on the image carrier in the developing area. In a two-component developing type developing device, an electric charge is given to a toner by mixing and stirring a toner and a magnetic carrier which are separated from each other on a frictional charging sequence. Control agents can liberate and contaminate the carrier surface. Therefore, when the carrier is used for a long period of time, the charging ability of the toner gradually decreases due to the influence of the charge control agent, so that there is a disadvantage that the developer needs to be replaced. In addition, a toner concentration control device and a developer stirring device for maintaining a constant mixing ratio between the toner and the carrier are required, and a magnet for supporting the magnetic carrier inside the developer carrier is required. There is a problem that the device becomes complicated.

On the other hand, a developing device of the one-component developing system is widely used because it does not have the above-mentioned disadvantages of the two-component developing system. In a one-component developing type developing device, a developer (toner) carrier is pressed against a toner layer forming member made of an elastic material called a blade,
2. Description of the Related Art A method of forming a thin toner layer on a toner carrier and applying a charge to toner by frictional charging between the toner layer and a toner layer forming blade has been widely adopted. However, in general, it is difficult to sufficiently charge the toner because the toner charging ability of the blade is low, so that a so-called reverse polarity toner charged to a polarity opposite to a desired polarity is easily generated. There is a drawback that fog often occurs. That is, in the triboelectric charging by the blade, the probability that the toner particles come into contact with the blade is low, and particularly, the minute toner may pass through the toner layer forming blade without being triboelectrically charged. In order to promote the triboelectric charging, it is conceivable to increase the pressing force of the toner layer forming blade against the toner layer.However, when the pressing force is increased, the binder resin of the toner melts due to an increase in frictional heat, and the aggregated toner May clog the blade and cause a problem that white streaks are generated in the image.

Therefore, in order to solve the above problems,
Japanese Patent Application Laid-Open Nos. Sho 54-17030 and 62-29, for example, disclose a developing device of a system for directly applying a charge to toner.
No. 1678, Japanese Unexamined Patent Publication No. Sho 64-62675, and the like. These developing devices will be described with reference to FIGS. FIG. 12 is a schematic configuration diagram illustrating an example of a conventional developing device.

A developing device 20 shown in FIG. 12 includes a toner carrier 22 disposed in close proximity to the image carrier 1 and rotating in the direction of arrow A, and a toner carrier for stirring toner in the developing device 20. A stirring and supplying member 24 for supplying toner to the surface 22
And a toner layer forming blade 23 that presses against the toner carrier 22 and forms the toner supplied by the stirring and supplying member 24 into a toner layer having a predetermined thickness, and contacts the toner carrier 22 or sets a minute interval. A cylindrical charging electrode 25 disposed at a distance; a bias power supply 27 for supplying a developing bias voltage to the toner carrier 22; a toner charging power supply 28 for supplying a toner charging voltage to the charging electrode 25; A housing 21 is provided for accommodating each of the components other than the power supply. Using the developing device 20 configured as described above, the charging electrode 25 is
A charging voltage is applied to the charging electrode 25 and the toner carrier 22.
A discharge electric field is formed in the gap between the toner and the toner, and ions or electrons generated by the discharge are attached to the toner to charge the toner.

The developing device of the type shown in FIG. 12 does not have the above-mentioned drawbacks of the triboelectric charging system, does not require a high voltage as high as a corona discharger, and generates less ozone because the applied voltage is low. Although it has advantages, it has the following problems. In other words, since the developing device of this type uses a toner having a high volume resistivity,
In the developing device 20 of FIG. 12, if the voltage applied to the charging electrode 25 is lower than the discharge voltage, the charge is not sufficiently induced, and the toner cannot be charged to a desired polarity. Therefore, it is conceivable to increase the voltage applied to the charging electrode 25 to a voltage equal to or higher than the discharging voltage to charge the toner by a discharging phenomenon from the charging electrode 25.
As will be described next, the toner is charged to the opposite polarity (positive in this case) to the desired polarity (minus in this case).

FIG. 13 is a diagram showing a charged state of the toner on the toner carrier in the developing device shown in FIG. As shown in FIG. 13, in the developing device 20 shown in FIG. 12, when the voltage applied to the charging electrode 25 is increased to cause the discharge, the discharge is generated between the charging electrode 25 and the toner carrier 22. An avalanche phenomenon occurs due to the accompanying ionization,
As a result, charge carriers having a positive polarity of positive ions 4 and charge carriers having a negative polarity of electrons or negative ions 3 are generated in the discharge region. As a result, the charged toner is in a state where the toner 2a charged to the desired polarity (minus) and the toner 2b charged to the opposite polarity (plus) are mixed. The opposite polarity refers to a positive polarity when the toner is to be negatively charged as in this example, but refers to a negative polarity when the toner is to be positively charged.

When such a reverse polarity toner is transported to the developing area by the toner carrier, the developed toner image is deteriorated in image quality such as background fog, and a good image cannot be obtained. Further, there is a problem that the opposite polarity toner scatters from the toner layer on the toner carrier and causes toner contamination in the apparatus.

[0010]

In order to solve the problem of the opposite polarity toner, an improved developing device of the charging electrode type shown in FIG. A developing device is conceivable in which a control electrode having a large number of openings is provided to limit the ionization region of an electric field generated between the charging electrode and the toner carrier, thereby preventing generation of toner of opposite polarity. In this developing device, a strong electric field is formed by applying a high voltage equal to or higher than the discharge starting voltage between the charging electrode and the control electrode, and a discharge is generated between the control electrode and the toner carrier. A weak electric field is formed by applying a low voltage. Thus, an ionization region is formed between the charging electrode and the control electrode, and positive and negative charge carriers such as positive ions, negative ions, and electrons are generated by an avalanche phenomenon. Due to the action of the electric field formed between the control electrode and the toner carrier, only the charge carrier of the desired polarity among the charge carriers of both positive and negative polarities is attracted to the toner carrier through the opening provided in the control electrode. As a result, the toner on the toner carrier can be charged only to a desired polarity, and the problem of the opposite polarity toner can be solved.

However, in a developing device having such a charging electrode and a control electrode, the charging efficiency greatly varies depending on the setting of the parameters such as the shape, structure, and applied voltage of the charging electrode and the control electrode. It is clear that if not appropriate, the charging efficiency is low and does not reach a practical level. Therefore, it is necessary to perform experiments on these parameters in various combinations to find the optimum conditions.

By the way, charging means of this type is
The present invention can be applied to a primary charger, a static eliminator, and a transfer device of an image forming apparatus. Conventionally, corona chargers have been widely used as primary chargers and static eliminators in image forming apparatuses.However, if a corotron charger is used, there is a problem that dirt adheres to the corotron wire and uniform charging cannot be obtained. May be. Further, in order to stably ionize the air layer near the corotron wire, it is necessary to apply a high voltage of 5 kV or more, and it is difficult to configure a small-sized and low-cost charger. Further, the corotron charger has a drawback that much ozone is generated.

Further, as a transfer device of the image forming apparatus,
Conventionally, a transfer device using the above-mentioned corotron charger, or a roll-type transfer device in which a transfer roll is pressed against a toner image carrier is widely used, but a corotron-type transfer device has the above-mentioned disadvantages. In addition, the roll-type transfer device has a problem that an image defect such as a missing image is likely to occur due to the toner image being pressed by the roll.

The present invention has been made in view of the above circumstances, and has as its object to provide a small developing device, a charging device, and a transfer device having high charging efficiency and low ozone generation.

[0015]

According to the present invention, there is provided a developing device for carrying an electrostatic latent image which moves in a predetermined direction to approach or contact an image carrier in a predetermined developing area. A toner carrier that carries the supplied toner on the surface and conveys the toner toward the development area, a toner layer forming member that forms the toner supplied to the toner carrier into a toner layer having a predetermined thickness, A first electrode disposed opposite to the toner carrier carrying the toner layer formed by the toner layer forming member; and a voltage having a predetermined polarity applied to the first electrode to apply a voltage to the toner carrier. A first power supply that forms an electric field between the first electrode and the first electrode; and a first power supply that is disposed between the first electrode and the member to be charged via an insulating layer between the first electrode and the first electrode. The ionization region of the discharge generated in the first electrode and the first electrode A second electrode having a large number of openings, regulated between the first and second electrodes; and a second voltage applied to the second electrode, the voltage forming an intermediate potential between the potential of the first electrode and the potential of the toner carrier. A voltage having a voltage of Vdis applied to the first electrode, a voltage of Vele applied to the second electrode, a thickness of the insulating layer Tins, and an opening of the second electrode. When the diameter of Dele is defined as Dele, 10 <(ΔV / Tins) exp (−0.2Dele /
(Tins) However, the relationship ΔV = | Vdis−Vele | is satisfied.

A charging device according to the present invention for achieving the above object is a charging device which moves relative to a predetermined charged object and charges the charged object. A first electrode disposed in proximity to the first electrode, a first power supply for applying a voltage of a predetermined polarity to the first electrode to form an electric field between the first electrode and the first electrode; Disposed between the first electrode and the member to be charged with an insulating layer interposed therebetween, and regulates an ionization region of a discharge generated in the electric field between the first electrode and the first electrode. A second electrode having a large number of openings, and a second power supply for applying to the second electrode a voltage forming an intermediate potential between the potential of the first electrode and the potential of the member to be charged. The voltage applied to the first electrode is Vdis, and the voltage applied to the second electrode is Vel.
e, when the thickness of the insulating layer is Tins and the diameter of the opening of the second electrode is Dele, 10 <(ΔV / Tins) exp (−0.2Dele /
(Tins) However, the relationship ΔV = | Vdis−Vele | is satisfied.

Further, according to the transfer device of the present invention, which achieves the above object, the transfer device is formed on a predetermined first toner image carrier.
A transfer device for transferring a toner image carrying a charge onto a predetermined second toner image carrier moving in close proximity to or in contact with the first toner image carrier at a predetermined transfer position. A first electrode disposed close to the second toner image carrier on a back side of the image carrier on a surface on which the toner image is transferred; and a charge carried by the toner image on the first electrode. A voltage having a polarity opposite to that of the first toner image carrier is applied to form a first power supply for forming an electric field with the second toner image carrier, and an insulating layer is interposed between the first power supply and the first electrode. A large number of apertures are provided at positions sandwiched between the first electrode and the second toner image carrier, and regulate an ionization region of a discharge generated in the electric field between the first electrode and the first electrode. And a second electrode having a potential of the first electrode and the first toner And a second power source for applying a voltage to form an intermediate potential between the potential of the image carrier, the first
When the applied voltage to the second electrode is Vdis, the applied voltage to the second electrode is Vele, the thickness of the insulating layer is Tins, and the diameter of the opening of the second electrode is Dele, 10 <(ΔV / Tins) exp (-0.2Dele /
(Tins) However, the relationship ΔV = | Vdis−Vele | is satisfied.

[0018]

Embodiments of the present invention will be described below. FIG. 1 is a schematic configuration diagram showing an embodiment in which the developing device of the present invention is used in an image forming apparatus. FIG. 1 shows an image carrier 1 that carries an electrostatic latent image and moves in the direction of arrow A, and a toner on the image carrier 1 by selectively transferring toner to the image carrier 1 in a developing area C. 1 shows an image forming apparatus including a developing device 10 that visualizes an electro-latent image to generate a developed image.

The developing device 10 includes a toner carrier 12 and
A toner layer forming blade 13, a stirring and supplying member 14, and a charger 15 are provided. In the developing device 10 configured as above, the toner in the developing device 10 is agitated by the rotation of the agitating / supplying member 14 and supplied to the surface of the toner carrier 12. The toner supplied to the surface of the toner carrier 12 is conveyed to a position facing the toner layer forming blade 13 as the toner carrier 12 rotates in the direction of arrow B, and is pressed by the toner layer forming blade 13. 1
2, a toner layer having a predetermined thickness is formed. Next, the toner layer is transported to a position facing the charger 15, and
To be negatively charged. The charged toner layer is further transported to the developing area C. A bias voltage is applied between the image carrier 1 and the toner carrier 12 by a developing bias power supply (not shown), and toner is transferred from the toner layer conveyed to the development area C to the image carrier 1. By the selective transfer, the electrostatic latent image on the image carrier 1 is visualized to generate a developed image.

A one-component toner is used in the developing device of the present embodiment. As the toner, a polarity controlling agent such as a pigment or a metal-containing azo dye is contained in various thermoplastic resins such as styrene resin, acrylic resin and polyester resin. Is dispersed and pulverized to a size of 3 to 20 μm by classification, and a charge control agent is externally added. As the charge control agent, fine particles of 0.1 μm or less, such as silica, alumina, and titanium, which have been subjected to a hydrophobic treatment, are used. Among them, hydrophobic silica is preferable. Further, a toner fluidity auxiliary may be externally added.

In the present embodiment, the toner carrier 12 is obtained by cutting an aluminum pipe having a diameter of 20 mm and then sandblasting the circumferential surface. Instead of sandblasting, a material whose surface is treated with an oxide film or a material whose surface is coated with a resin in which a conductive material is dispersed may be used. As the toner layer forming member 13, a member obtained by vulcanizing and bonding silicone rubber or EPDM rubber to a stainless plate spring having a thickness of about 0.03 to 0.3 mm is used. The rubber having a hardness in the range of 20 to 80 degrees can be used, and the hardness in the range of 30 to 60 degrees is particularly preferable. The contact pressure of the toner layer forming member 13 to the toner carrier 12 is set to about 5 to 100 g / cm. As a result, the toner is formed in a thin layer of about 5 to 30 μm.

As the image carrier 1, a Se-based photoconductor or an organic photoconductor is generally used. The image carrier 1 and the toner carrier 12 may be arranged in contact with each other, or 100 to 40.
They may be arranged facing each other with a gap of about 0 μm. next,
Details of the charger 15 will be described with reference to FIGS. FIG. 2 is a partially enlarged view of a charger used in the developing device of the present embodiment.

As shown in FIG. 2, the charger 15 has an integral structure in which a charging electrode 15a, an insulating layer 15c, and a control electrode 15b are laminated, and the control electrode 15b faces the toner carrier 12. Are arranged as follows. A large number of fine openings 1 are provided in the control electrode 15b and the insulating layer 15c.
5d is formed. In addition, in FIG.
The dimension shown as le represents the diameter of the opening 15d, and the arrow T
The dimension indicated as ins represents the thickness of the insulating layer 15c. Dedicated power supplies 18a and 18b are connected to the charging electrode 15a and the control electrode 15b, respectively, and a predetermined voltage as described later is applied.

FIG. 3 is a plan view and a sectional view showing various embodiments of the charger used in the developing device of this embodiment. As shown in FIGS. 3A to 3D, the charger 1
5 has two types of electrodes, a charging electrode 15a and a control electrode 15b, and the charging electrode 15a and the control electrode 15b are integrally formed as a laminated body with an insulating layer 15c interposed therebetween. The control electrode 15b of the charger 15 is connected to the toner carrier 12
(See FIG. 1).

The control electrode 15b and the insulating layer 15c include:
Many fine openings 15d are formed. Opening 15d
3 (a), diagonal stripes as shown in FIG. 3 (b), circular shapes as shown in FIG. 3 (c), and FIG. Various shapes such as a rectangular shape as shown in d) can be adopted.

The charging electrode 15a is made of a semiconductive material, for example, a material obtained by dispersing a conductive material in an insulator, or an ionic conductive material having a volume resistivity of 10 ⁵ Ω · cm to 10 ⁵ Ω · cm.
^The one adjusted to ¹⁰ Ω · cm is used.
It is preferable to set the resistance to 0 ⁷ Ω · cm to 10 ⁸ Ω · cm. The control electrode 15b is obtained by forming a large number of openings 15d as shown in FIGS. 3A to 3D in a thin film produced by photoetching, electroforming, laser processing, or the like.

The insulating layer 15c is to insulate the charging electrode 15a and the control electrode 15b at a predetermined distance from each other, and is formed of an organic material such as polyimide or nylon, or an inorganic material such as glass. You may make it. Alternatively, the charging electrode 15a and the control electrode 1 are controlled such that a predetermined distance is maintained between the charging electrode 15a and the control electrode 15b.
5b may be formed to form an insulating layer (gap). In this embodiment, a stainless steel foil is used for the control electrode 15b, and the control electrode 15b has a thickness of 1 as the insulating layer 15c.
After laminating 0 μm polyimide and integrating them, a hole having a diameter of 80 μm is opened by etching.

A dedicated power supply (described later) is connected to each of the charging electrode 15a and the control electrode 15b.
A high voltage is applied between 5a and control electrode 15b, and a strong electric field sufficient to cause a discharge is applied to form an ionized region. In this ionization region, both charge carriers having a positive charge and charge carriers having a negative charge are generated by the avalanche phenomenon. On the other hand, a negative low voltage is applied between the control electrode 15b and the toner carrier 12 (see FIG. 1), and a weak electric field that does not cause discharge is formed. No ionized regions are formed here and no charge carriers are generated. However, due to the effect of the weak electric field formed between the control electrode 15b and the toner carrier, only the negatively charged carrier among the positive and negative charge carriers is guided toward the toner carrier, and the toner carrier The upper toner layer is negatively charged.

Referring back to FIG. 1, the toner layer charged by the charger 15 as described above is transported to the developing area C as the toner carrier 12 rotates in the direction B. A -200 V developing bias voltage is applied between the image carrier 1 and the toner carrier 12 by a bias power supply (not shown), and toner is selected for the image carrier 1 from the toner layer transported to the developing area C. As a result, the electrostatic latent image on the image carrier 1 is visualized to generate a developed image. In addition, instead of the DC voltage, a voltage in which an alternating component is superimposed on a DC component may be used as the developing bias voltage to ensure good developing performance.

In the present embodiment, the potential between the potential of the control electrode 15b and the potential of the toner carrier 12 and the potential of the charging electrode 15a
And the potential of the control electrode 15b hold the following relationship. (Toner carrier potential)-(control electrode potential) = 500 V (control electrode potential)-(charging electrode potential) = 2000 V Specifically, -200 V for toner carrier 12, -700 V for control electrode 15b, and charging electrode -2700 for 15a
A voltage of V is applied.

As described above, in this developing device, not only the voltage applied to the charging electrode and the control electrode but also the combination of these applied voltages and parameters such as shape and structure determine the charging efficiency. Since it is clear that the parameters are the elements, the optimum conditions for these parameters are obtained as follows. Here, the voltage applied to the charging electrode 15a is Vdis, the voltage applied to the control electrode 15b is Vele, the thickness of the insulating layer 15c is Tins,
The diameter of the opening 15d of the control electrode is defined as Dele (see FIG. 2).

FIG. 4 is an equipotential diagram obtained by simulating the potential distribution of the charger shown in FIG. FIG.
4A to 4C, as the diameter Dele of the opening 15d of the control electrode 15b is increased, the charging electrode 15a and the control electrode 15b are increased.
The distance between the equipotential lines formed in the ionization region between them gradually increases, that is, the electric field intensity in the ionization region decreases. Therefore, efficient discharge is not performed, and the toner cannot be charged efficiently.

As factors for determining the charging efficiency, in addition to the diameter Dele of the opening 15d of the control electrode 15b, the thickness Tins of the insulating layer 15c, the voltage Vdis applied to the charging electrode and the voltage applied to the control electrode 15b. It is known that the potential difference ΔV (= | Vdis−Vele |) from the applied voltage Vele has a close relationship with each other. Therefore, as a parameter, a potential difference ΔV (= | Vdi) between the voltage Vdis applied to the charging electrode and the voltage Vele applied to the control electrode is used.
s-Velle |), insulating layer thickness Tins, control electrode 15
Ratio of opening diameter Dele of b to insulating layer thickness Tins: De
Le / Tins was calculated, and an approximate expression representing the relationship between these parameters and the electric field strength E near the charging electrode 15a on the center line of the opening 15c of the control electrode 15b in FIG. 4 was obtained by simulation. As a result of the simulation,
It can be seen that there is a relationship as shown in FIG. 5 between the electric field strength E and Dele / Tins.

FIG. 5 is a graph showing the result of a simulation calculation of the electric field strength in the ionization region of the charger of FIG. When the approximate expression of the value E on the vertical axis and the value Dele / Tins on the horizontal axis is derived from the plot on this graph, the following expression is derived. E = (ΔV / Tins) exp (−0.2x) x = Dele / Tins FIG. 6 shows the electric field intensity E obtained from the approximate expression obtained from FIG.
6 is a graph showing the relationship between the thickness of the insulating layer Tins and the charged state of the toner. The charged state of the toner is CSG
(Charge Spectro Graphy).

As shown in FIG. 6, there is no clear correlation between the charged state of the toner and the thickness Tins of the insulating layer, but when the electric field intensity E is sufficiently large, the toner is sufficiently charged. It can be seen that the toner is not charged satisfactorily when the electric field strength E is small. From these results, in order to charge the toner by the developing device of this embodiment, 10 <(ΔV / Tins) exp (−0.2Dele /
However, it is necessary that the relationship of ΔV = | Vdis−Vele | be satisfied, and to sufficiently charge the toner, 25 <(ΔV / Tins) exp (−0.2Dele /
However, it is preferable that the relationship of ΔV = | Vdis−Vele | is satisfied.

By doing so, the toner can be charged with high charging efficiency using the charger of the developing device of the present embodiment. The thickness of the insulating layer 15c sandwiched between the charging electrode 15a and the control electrode 15b is such that the toner can be charged under the condition that the above relationship is satisfied. In addition, the voltage Vdis applied to the charging electrode needs to be higher than the discharge starting voltage. However, if the applied voltage Vdis is too high, problems such as dielectric breakdown may occur. Therefore, it is preferable that the thickness of the insulating layer 15c is not too thick.

FIG. 7 is a graph of the discharge starting voltage obtained from Paschen's equation. FIG. 7 is a graph in which the horizontal axis represents the thickness Tins of the insulating layer, and the vertical axis represents the firing voltage ΔV (| Vdis−Vele |) obtained by Paschen's equation. As shown in FIG. 7, the thickness Tins of the insulating layer
Is 700 μm, the discharge starting voltage ΔV is about 450
It turns out that 0V is required. In order not to require a special large power supply as a power supply for the charger, the voltage applied to the charging electrode must be equal to or lower than that of a conventional discharger, for example, 4500 V or less. Requires that the thickness of the insulating layer be 700 μm or less, more preferably 200 μm or less.

Next, the results of a toner charging experiment performed using the charging device having the above-described configuration will be described. The preferable charge amount in the toner charger of the present embodiment is when the toner is charged to −7 μC / g or more by one charging.
The preferable charge amount is slightly different depending on the particle size, material, density, etc. of the toner.
The toner was charged in the range of -7 μC / g to -12 μC / g, and only 0.1 wt% or less of the opposite polarity toner was generated.

Further, a long-time print test was performed under the following conditions using an image forming apparatus using the same charger as described above. Latent image carrier: negatively charged organic photoreceptor Process speed: 200 mm / sec Control electrode: A fine aperture having a diameter of 80 μm is formed on a film made of a conductive material having a thickness of 100 μm by an aperture ratio of 80.
% Charged electrode: rubber containing electronic conductor, hardness 6
0 ° and volume resistivity of 10 ⁷ Ω · cm Toner carrier: aluminum roll having a diameter of 20 mm,
Surface roughness Ra = 0.5 Toner supply member: Roll made of semiconductive sponge material having a diameter of 10 mm Toner layer forming member: SUS303 having a thickness of 0.12 mm
A 1 mm-thick EPDM rubber was bonded to a leaf spring having a rubber hardness of 50, a bonding pressure of about 30 gf / cm, and a volume resistivity of 10 ⁵ Ωcm. Latent image potential: -100 V Blank paper section potential: -350 V As a result of a print test, the toner was sufficiently charged, and there were no problems such as background fogging and toner scattering in the apparatus due to the opposite polarity toner, which were the conventional problems, and stable image formation was possible.

Next, an embodiment of the charging device of the present invention will be described. FIG. 8 is a schematic configuration diagram showing an embodiment in which the charging device of the present invention is used as a primary charger of an image forming apparatus. FIG. 8 shows an image carrier 1 rotating in the direction of arrow A.
And a primary charger 50 for uniformly charging the surface of the image carrier 1
An electrostatic latent image forming device 9 for forming an electrostatic latent image based on an image on the primary charged image carrier 1, and developing the electrostatic latent image formed on the image carrier 1 to carry the image A developing device 10 for forming a toner image on the body 1, a developing high-voltage power supply 11 for applying a developing bias voltage to the developing device 10, and a transfer medium for transferring the toner image formed on the image carrier 1 in a transfer area T. 6
The image forming apparatus includes a transfer device 60 that transfers the transfer medium 6 to the transfer medium 6 and a sheet conveying device 66 that supplies the transfer medium 6 to the transfer area T.

The primary charger 50 in the present embodiment corresponds to the charging device according to the present invention, and the image carrier 1 in the present embodiment corresponds to the member to be charged of the charging device according to the present invention. It is. The primary charger 50 is a device for uniformly charging the surface of the image carrier 1 prior to a process of forming an electrostatic latent image on the image carrier 1 by the electrostatic latent image forming device 9. The primary charger 50 includes a first electrode 51 disposed in close proximity to the image carrier 1 to which electric charges are supplied, and a voltage of a predetermined polarity applied to the first electrode 51 to form a contact between the first electrode 51 and the image carrier 1. A first power supply 53 for forming a strong electric field between the first power supply 53 and the first electrode 5
A second electrode 52 having a large number of openings, which is provided at a position sandwiched between the first electrode 51 and the image carrier 1 and regulates an ionization region of a discharge generated in the electric field between the first electrode 51 and the second electrode 52. , Second
And a second power supply 54 for applying a voltage that forms an intermediate potential between the potential of the first electrode 51 and the potential of the image carrier 1.

The primary charging device 50 is substantially the same as the charging device 15 of the developing device 10 described with reference to FIGS. 1 to 3 in that the first electrode 51 and the second electrode 52 have a predetermined thickness. It is formed as an integrated structure laminated with an insulating layer interposed therebetween, and has various embodiments similar to those shown in FIG. In the primary charger 50 of the present embodiment, the charger 1 of FIG.
5, the voltage applied to the first electrode 51 is Vd
is, the voltage applied to the second electrode 52 is Vele, the thickness of the insulating layer is Tins, and the diameter of the opening of the second electrode is D
ele, 10 <(ΔV / Tins) exp (−0.2Dele /
However, each parameter is set so as to satisfy the relationship of ΔV = | Vdis−Vele |.

FIG. 9 is a graph showing the relationship between the electric field intensity E of the primary charger shown in FIG. 8, the rotation speed of the member to be charged, and the charged state of the image carrier. As shown in FIG. 9, the electric field strength E slightly increases to the right by increasing the rotation speed of the member to be charged (the image carrier 1 in FIG. 8). It can be seen that は increases substantially in proportion to the electric field strength E. From the results shown in FIG. 9, in order to charge the member to be charged by the charging device of this embodiment, 10 <(ΔV / Tins) exp (−0.2Dele /
However, the relationship ΔV = | Vdis−Vele | needs to be satisfied, and in order to sufficiently charge the member 1 to be charged, 15 <(ΔV / Tins) exp (−0.2Dele /
Tins) However, it is preferable to satisfy the relationship of ΔV = | Vdis−Vele |.

Thus, the charged object can be charged with high charging efficiency using the charging device of the present embodiment. Also, since this charging device does not use a high voltage unlike a corotron charger, the amount of generated ozone is small,
A small and low-cost charging device can be configured. Next, an embodiment of the transfer device of the present invention will be described.

FIG. 8 used in describing the charging device of the present invention also shows an embodiment in which the transfer device of the present invention is used in an image forming apparatus. Next, an embodiment of the transfer device of the present invention will be described. As described above, the image forming apparatus shown in FIG. 8 includes the image carrier 1 rotating in the direction of arrow A, the primary charger 50 for uniformly charging the surface of the image carrier 1, and the primary charged image carrier. An electrostatic latent image forming apparatus 9 for forming an electrostatic latent image based on an image on the body 1, and an image carrier 1 by developing the electrostatic latent image formed on the image carrier 1
Developing device 10 for forming a toner image thereon; developing device 10
Developing high-voltage power supply 11 for applying a developing bias voltage to
And a transfer device 60 that transfers the toner image formed on the image carrier 1 to the transfer medium 6 in the transfer area T, and a paper transport device 66 that supplies the transfer medium 6 to the transfer area T.

The transfer device 60 is disposed to face the first toner image carrier 1 almost immediately below the first toner image carrier 1 of the image forming apparatus with a gap of about 2 mm therebetween. At the transfer position T, the toner image formed on the image carrier 1 is transferred onto a transfer medium 6 that moves in proximity to or in contact with the image carrier 1. Note that the image carrier 1 of the present embodiment corresponds to the first toner image carrier of the transfer device according to the present invention, and the transfer medium 6 of the present embodiment corresponds to the second toner image carrier of the transfer device according to the present invention. It corresponds to a toner image carrier. The combination of the first toner image carrier and the second toner image carrier in the transfer device of the present invention is as follows.
The present invention is not limited to the above combination, and may be, for example, a combination in which the first toner image carrier is an image carrier and the second toner image carrier is an intermediate transfer drum.
Further, the first toner image carrier is an intermediate transfer drum and
May be used as a transfer medium.

The transfer device 60 has a first electrode 61
, A first electrode 62, a second power supply 63, a second power supply 64, and a paper pressing plate 65. The first electrode 61 is disposed on the back side of the surface of the transfer medium 6 to which the toner image is transferred, in the vicinity of the transfer medium 6, and the first power supply 63 By applying a polarity voltage, a transfer electric field is formed between the transfer medium 6 and the transfer medium 6. The second electrode 62 has a large number of openings (described later).
And is disposed at a position sandwiched between the first electrode 61 and the transfer medium 6, and regulates the ionization region of the discharge generated in the electric field between the first electrode 61 and the transfer medium 6. Second power supply 6
4 applies to the second electrode 62 a voltage that forms an intermediate potential between the potential of the first electrode 61 and the potential of the image carrier 1. When the transfer medium 6 is conveyed to the transfer position T in the transfer device 60 thus configured, the paper pressing plate 65 presses the leading end of the transfer medium 6 against the image carrier 1. As a result, the transfer medium 6 is supplied to the nip portion formed by the image carrier 1 and the second electrode 62 at the transfer position T in a state of being in close contact with the image carrier 1. Since the transfer medium 6 has no charge, it passes through the nip portion of the transfer device 60 while being electrostatically attracted to the charged image carrier 1.

FIG. 10 is a partially enlarged view of the transfer device shown in FIG. As shown in FIG. 10, the first electrode 61 is formed in a plate shape, and on the surface thereof, an insulating layer 61a having the same planar shape as the first electrode 61 main body is laminated. The first electrode 61 is made of a material containing an ionic conductor or silicone rubber mixed with conductive fine particles to have a volume resistivity of 10%.
Those adjusted to about ⁵ to 10 ¹⁰ Ω · cm are used.
A semiconductive glass electrode plate may be used for the first electrode 61, and the volume resistivity in that case is 10 ⁷ to 10 ⁸ Ω · c.
m is preferable.

The second electrode 62 is made of a stainless mesh member having a wire diameter of 50 μm and a pitch of 127 μm, and has the same outer shape as the insulating layer 61a. In this case, the mesh of the mesh corresponds to the opening of the second electrode 62. The second electrode 62 is not limited to the mesh-shaped member, and may be a plate-shaped stainless member provided with a large number of openings, in which case the diameter of the openings is 10 μm to 300 μm, and the thickness is 10 μm to 100 μm. The degree is appropriate.

In this embodiment, since the transfer medium 6 is charged with a charge opposite to that of the negatively charged toner, a stronger electric field is applied between the first electrode 61 and the second electrode 62 by a high voltage equal to or higher than the discharge starting voltage. Is formed between the second electrode 62 and the transfer medium 6 with a weak electric field that does not cause a discharge and in a direction in which positive charges are attracted to the transfer medium 6. The following relationship is maintained between the potential of the image carrier 1 and the potential of the second electrode 62, and between the potential of the first electrode 15a and the potential of the second electrode.

(Image Carrier Potential) − (Second Electrode Potential) = 600 V (Second Electrode Potential) − (First Electrode Potential) = 1700 V The image carrier 1, first electrode 61, and Each potential of the second electrode 62 is appropriately adjusted depending on the distance between the transfer device 60 and the toner image on the image carrier 1, the structure and thickness of the second electrode 62, and the like. The first electrode 61 and the second electrode 6
When the image carrier 2 and the image carrier 1 are arranged with a gap therebetween, the size of the gap is determined in consideration of the gap. In the present embodiment, the surface of the image carrier 1 is charged to −700 V by the discharge of the primary charger 50,
A DC voltage of 2.5 KV is applied to the first electrode 63 from the first power supply 63, and the second power supply 64 is applied to the second electrode 62.
To 800V DC voltage is applied. These DC voltages are applied with a polarity opposite to the charging polarity of the toner.

When the toner image formed on the image carrier 1 reaches the transfer position T of the transfer device 60 thus configured, the toner image has a polarity opposite to that of the toner (positive in this case). The transfer medium 6 is attracted to the charged transfer medium 6 by the ions, and the transfer medium 6 is charged, and the toner image is transferred to the transfer medium 6. Also in the transfer device 60 of the present embodiment, the voltage applied to the first electrode 61 is Vdis, the voltage applied to the second electrode 62 is Vele, the thickness of the insulating layer 61a is Tins, and the voltage applied to the second electrode 62 is When the diameter of the opening is Dele, 10 <(ΔV / Tins) exp (−0.2Dele /
However, each parameter is set so as to satisfy the relationship of ΔV = | Vdis−Vele |.

FIG. 11 is a graph showing the relationship between the electric field intensity E of the transfer device shown in FIG. 10, the process speed, and the charged state of the image carrier. As shown in FIG. 11, as the process speed, that is, the rotation speed of the image carrier 1 is increased, the electric field intensity E tends to slightly increase to the right, but the charge amount of the member to be charged (image carrier) is increased. It can be seen that は increases substantially in proportion to the electric field strength E. From the results shown in FIG. 11, in order to charge the member to be charged by the transfer device of this embodiment, 10 <(ΔV / Tins) exp (−0.2Dele /
However, it is necessary that the relationship of ΔV = | Vdis−Vele | be satisfied, and further, in order to sufficiently charge the member to be charged, 30 <(ΔV / Tins) exp (−0.2Dele /
Tins) However, it is preferable to satisfy the relationship of ΔV = | Vdis−Vele |.

By doing so, the transfer medium can be charged with high charging efficiency using the transfer device of the present embodiment. In addition, since this transfer device does not use a high voltage unlike a corotron charger, the amount of ozone generated is small,
A compact and low-cost transfer device can be configured. In this transfer device 60, the transfer medium 6 is
Since there is no contact with the toner image, there is no pressing force on the toner image to be transferred on the image carrier 1 and the transfer medium 6, and therefore, when the toner image is transferred, a hollow portion may occur at the center of the image. Absent. As a transfer method in which the transfer device and the transfer belt are not in contact with each other, there is a transfer method using discharge using a corotron as a conventional technique, but as described above, a large amount of ozone is inevitable in the corotron method, Further, since a shield block surrounding the discharge line is required, it is not possible to meet the demand for downsizing the transfer device, and the transfer toner image often scatters. In contrast, the transfer device of the present invention can solve all of these problems.

[0055]

As described above, according to the developing apparatus of the present invention, the applied voltage Vdis to the first electrode, the applied voltage Vele to the second electrode, the thickness Tins of the insulating layer, the control electrode By appropriately setting the relationship between the parameters of the opening diameter Dele, it is possible to obtain a small developing device having high charging efficiency and low ozone generation. The amount of ozone generated by the developing device of the present invention is 1/100 to 1/1 of that when a conventional corotron or scorotron charger is used.
It is about 000.

Further, according to the charging device of the present invention, a small charging device having a high charging efficiency and a small ozone generation amount can be obtained by appropriately setting the relationship between the parameters as in the developing device. be able to. According to the transfer device of the present invention, as in the developing device,
By appropriately setting the relationship between the parameters, it is possible to obtain a small-sized transfer device having a high charging efficiency and a small ozone generation amount.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment when a developing device of the present invention is used in an image forming apparatus.

FIG. 2 is a partially enlarged view of a charger used in the developing device of the embodiment.

FIG. 3 is a plan view and a sectional view showing various embodiments of a charger used in the developing device of the present embodiment.

FIG. 4 is an equipotential diagram obtained by simulating a potential distribution of the charger shown in FIG. 2;

FIG. 5 is a graph showing a result obtained by a simulation calculation of an electric field intensity in an ionization region of the charger of FIG. 2;

6 is an electric field intensity E obtained from the approximate expression obtained from FIG.
6 is a graph showing the relationship between the thickness of the insulating layer Tins and the charged state of the toner.

FIG. 7 is a graph of a discharge starting voltage obtained from Paschen's equation.

FIG. 8 is a schematic configuration diagram showing an embodiment in which the charging device of the present invention is used as a primary charger of an image forming apparatus.

9 is a graph showing the relationship between the electric field intensity E of the primary charger shown in FIG. 8, the rotation speed of the member to be charged, and the charged state of the image carrier.

FIG. 10 is a partially enlarged view of the transfer device shown in FIG.

11 is a graph showing a relationship among an electric field intensity E, a process speed, and a charged state of an image carrier of the transfer device shown in FIG.

FIG. 12 is a schematic configuration diagram illustrating an example of a conventional developing device.

13 is a diagram illustrating a charged state of toner on a toner carrier in the developing device illustrated in FIG. 12;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image carrier 2, 2a, 2b Toner 3 Electron or negative ion 4 Positive ion 6 Transfer medium 9 Electrostatic latent image forming apparatus 10 Developing device 11 High voltage power supply for development 12 Toner carrier 13 Toner layer forming blade 14 Stirring supply member 15 Charger 15a Charging electrode 15b Control electrode 15c Insulating layer 15d Opening 18a, 18b Power supply 20 Developing device 21 Housing 22 Toner carrier 23 Toner layer forming blade 24 Stirring supply member 25 Charging electrode 27 Bias power supply 28 Toner charging power supply 50 Primary charger 51 first electrode 52 second electrode 53 first power supply 54 second power supply 60 transfer device 61 first electrode 62 second electrode 63 first power supply 64 second power supply 65 paper pressing plate 66 paper transport apparatus

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shinichi Kuramoto 430 Sakai Nakaicho, Ashigara-gun, Kanagawa Green Tech Nakai Inside Fuji Xerox Co., Ltd. In company

Claims (3)

[Claims] An image bearing member that carries an electrostatic latent image and moves in a predetermined direction is arranged so as to be close to or in contact with an image carrier in a predetermined development region, and carries the supplied toner on the surface thereof to form the development region. , A toner layer forming member for forming the toner supplied to the toner supporting member into a toner layer having a predetermined thickness, and a toner layer formed by the toner layer forming member. A first electrode disposed opposite to the toner carrier, a first power supply for applying a voltage of a predetermined polarity to the first electrode to form an electric field between the first electrode and the toner carrier, The first electrode is disposed at a position sandwiched between the first electrode and the member to be charged with an insulating layer interposed between the first electrode and the first electrode, and an ionization region of a discharge generated in the electric field is formed between the first electrode and the first electrode. A second electrode having a number of openings for regulating between A second electrode provided with a charger having a second power supply for applying a voltage for forming an intermediate potential between the potential of the first electrode and the potential of the toner carrier; Is Vdis, the voltage applied to the second electrode is Vele, and the thickness of the insulating layer is Tin.
s, when the diameter of the opening of the second electrode is Dele, 10 <(ΔV / Tins) exp (−0.2Dele /
Tins) However, the developing device is characterized in that a relationship of ΔV = | Vdis-Vele | is satisfied. 2. A charging device which moves relative to a predetermined member to be charged and charges the member to be charged, comprising: a first electrode arranged in proximity to a member to be charged with a charge; A first power supply for applying a voltage of a predetermined polarity to the first electrode to form an electric field between the first electrode and the member to be charged; and a first power supply via an insulating layer between the first electrode and the first electrode. A second electrode having a large number of openings, which is provided at a position sandwiched between the first electrode and the object to be charged, and regulates an ionization region of discharge generated in the electric field between the first electrode and the second electrode. A second power supply for applying a voltage that forms an intermediate potential between the potential of the first electrode and the potential of the member to be charged, to the second electrode, and applying a voltage to the first electrode. The voltage is Vdis, the voltage applied to the second electrode is Vele, and the thickness of the insulating layer is Tin.
s, when the diameter of the opening of the second electrode is Dele, 10 <(ΔV / Tins) exp (−0.2Dele /
Tins) However, the charging device is characterized in that a relationship of ΔV = | Vdis-Vele | is satisfied. 3. A method for moving a toner image carrying an electric charge, formed on a predetermined first toner image carrier, to a position close to or in contact with the first toner image carrier at a predetermined transfer position. A transfer device for transferring the toner image on the second toner image carrier, wherein the second toner image carrier has a back surface side with respect to a front surface on which the toner image is transferred, and is provided in close proximity to the second toner image carrier. Applying a voltage having a polarity opposite to the polarity of the electric charge carried by the toner image to the first electrode provided, and applying an electric field between the first electrode and the second toner image carrier; A first power supply for forming a first power supply and a first power supply, the first power supply being disposed between the first electrode and the second toner image carrier via an insulating layer between the first power supply and the first electrode; A second electrode having a large number of openings for regulating an ionization region of a discharge generated between the first electrode and the first electrode; And a second power supply for applying to the second electrode a voltage that forms an intermediate potential between the potential of the first electrode and the potential of the first toner image carrier, The voltage applied to the first electrode is Vdis, the voltage applied to the second electrode is Vele, and the thickness of the insulating layer is Tin.
s, when the diameter of the opening of the second electrode is Dele, 10 <(ΔV / Tins) exp (−0.2Dele /
Tins) However, the transfer device is characterized in that a relationship of ΔV = | Vdis−Vele | is satisfied.