JPH07175318A - Developing device and process cartridge - Google Patents

Abstract

PURPOSE:To obtain an excellent image without reversal fogging by increasing a chance to bring the developer electrostatically charged to have a reverse polarity into contact with the surface of a developer carrier at the abutting part of a developer regulating member on the developer carrier and realizing normally electrostatically charging the developer. CONSTITUTION:A developing blade 1 is provided with a soft nonconductive elastic member 1a, a conductive layer 1b laminated and supported on the member 1a, and a dielectric layer 1c arranged on an opposed surface to a developing sleeve 3. By setting an electric field generating means and impressing voltage on the conductive layer 1b, the electric field E is pulsatively generated so that force attracting the normally electrostatically charged toner T1 to the surface of the blade 1 may act at the nip 4 of the abutting part. Since the blade 1 has soft elasticity, the toner T is not in a packing state at the nip 4, and the chance to bring the reversal toner T2 into contact with the surface of the sleeve 3 by the force caused by the pulsatively imparted electric field E is increased, then the reversal toner T2 is normal electrostatically charged and reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device and a process cartridge used in an image forming apparatus using electrophotography.

[0002]

2. Description of the Related Art A conventional image forming apparatus has a structure as shown in FIG. In FIG. 10, reference numeral 100 denotes a photosensitive drum that is an image carrier, and the image forming apparatus includes a primary charger 117, a developing device 140, a registration roller 124, and a transfer charger 11 around the photosensitive drum 100.
4 and a cleaner 116 are provided.

The photosensitive drum 100 is charged by a primary charger 117, and a laser beam 1 is emitted from a laser scanner 121.
By exposing and exposing 23, the photosensitive drum 100
An electrostatic latent image is formed on it. The latent image on the photosensitive drum 100 is developed by the developing device 140 with a negative charging toner of a one-component developer to be visualized as a toner image, and the obtained toner image is transferred to the photosensitive drum 1 by the registration roller 124.
The transfer charger 114 electrostatically transfers the transfer material P onto the transfer material P transported to 00.

The transfer material P on which the toner image has been transferred is conveyed to a fixing device 126 by a conveyor belt 125, where the toner is melted by heating and pressurization and is solidified and fixed on the fibers of the transfer material P.

As shown in FIG. 11, the developing device 140 includes a developing container 140a containing an insulating magnetic toner T (in this example, the negative charging toner as described above) which is an insulating one-component magnetic developer. And a cylindrical developing sleeve 102, which is a developer carrying member, is disposed in the developing container 140a in proximity to the photosensitive drum 100. The developing sleeve 102 is made of non-magnetic metal such as aluminum and stainless steel. The gap between the photosensitive drum 100 and the developing sleeve 102 is maintained at about 300 μm by a gap regulating member (not shown).

A magnet roller 104, which is a magnetic field generating means, is concentrically arranged in the developing sleeve 102 with a gap therebetween. The magnet roller 104 is fixed to the main body of the image forming apparatus and is non-rotatable.
Rotates around the built-in magnet roller 104.

As shown in the drawing, the magnet roller 104 is
Four magnetic poles S1, S2, N1, N2 are provided.
The magnetic pole S1 is a developing pole, the magnetic pole N1 is a toner amount regulating pole, and the magnetic pole S is
Reference numeral 2 is a toner intake / conveyance pole, and magnetic pole N2 is a pole for preventing toner blowout.

The magnetic toner T contained in the developing container 140a is carried on the developing sleeve 102 by being attracted by the magnetic force of the magnet roller 104 inside the developing sleeve 102, and the photosensitive drum 1 is rotated by the rotation of the developing sleeve 102 in the arrow B direction.
The sheet is conveyed toward the developing area facing 00.

A container 140a above the developing sleeve 102.
At the position of, the elastic blade 10 is used as a toner amount regulating member.
3 is fixed, the elastic blade 103 hangs down on the developing sleeve 102 and elastically abuts on the developing sleeve 102.
The toner on 2 is regulated to form a thin toner layer, and the amount of toner conveyed to the developing area is regulated. The amount of toner conveyed to the developing area is determined by the contact pressure and contact length of the elastic blade 103 that contacts the developing sleeve 102. Conventionally, the amount of toner conveyed is controlled to about 1.0 to 2.0 mg / cm ² per unit surface area of the developing sleeve 102.

The toner conveyed to the developing area is
By the developing electric field generated by the developing bias applied between the developing sleeve 102 and the photosensitive drum 100, the developing sleeve 1
02 flying from above onto the photosensitive drum 100 rotating in the direction of arrow A, adhering to the latent image on the photosensitive drum 100 to develop,
The latent image is visualized as a toner image.

In addition to the above, an insulating one-component non-magnetic developer (insulating non-magnetic toner) or a two-component developer obtained by mixing an insulating non-magnetic toner with a magnetic carrier,
There is a developing device that uses a two-component developer in which a non-magnetic carrier or a magnetic carrier is mixed with an insulating magnetic toner.
Since it is already known to the world, its explanation is omitted.

[0012]

In the developing device shown in FIG. 11, the charged electric charge held by the magnetic toner T is the toner T.
Although it is obtained by frictional charging between the elastic blade 103 and the developing sleeve 102, it has been found that there are the following problems.

The charging polarity of the toner T is determined by the material of the toner itself and the materials of the developing sleeve 102 and the elastic blade 103. Further, the charging of the toner also depends on the type and amount of the external additive added to the toner, the contact pressure of the elastic blade 103 with the developing sleeve 102, and the contact width. For example, in order to charge the toner to a negative polarity, a resin of the toner having a negative polarity in the charging series may be used, and a material of the elastic blade 103 and the developing sleeve 102 may have a positive polarity in the charging series.

However, in reality, in addition to the triboelectrification of the toner with the developing sleeve and the elastic blade, the triboelectrification of the toners also occurs. As a result, in addition to the negatively charged toner (regular toner), the oppositely charged positively charged toner (reversed toner) is generated. The amount of the reverse toner generated is usually about 10% of the total toner, which is smaller than the amount of negatively charged toner, and the total amount of toner applied on the developing sleeve is as follows.
The charge shows a negative polarity.

However, when the reverse toner is present,
Undesired adhesion of the reverse toner to the non-image area (white image area) causes fog, and the whiteness of the white image area is significantly reduced, deteriorating the image quality. Hereinafter, the phenomenon in which fogging occurs due to the reverse toner will be described in detail.

An image was formed using the image forming apparatus shown in FIG. By applying -700V to the primary charger 117, the surface of the photosensitive drum 100 is -700V.
Charged by the laser scanner 121 and exposed by the laser scanner 121.
An electrostatic latent image of 0 V was formed. Negative insulating magnetic toner is used in the developing device 140 of FIG. 11, and the developing sleeve 102 is applied with a DC voltage of −500 V and a frequency of 180.
A developing bias superposed with an alternating voltage of 0 Hz and a peak-to-peak voltage of 1640 V was applied. Photosensitive drum 100 at this time
FIG. 12 shows the relationship between the upper potential and the potential on the developing sleeve 102.
Shown in. In FIG. 12, non-image area potential on drum: V _D = -700 V Image area potential on drum: _VL = -150 V Development acceleration maximum voltage (maximum voltage value on the negative side of superimposed voltage of DC and AC): Vmax =- 1320V Development pullback maximum voltage (maximum voltage value on the plus side of the superimposed voltage of DC and AC): Vmin = + 320V AC peak-to-peak voltage: Vpp = 1640V Development contrast: Vcont = | _VDC |-| _VL |
It is 350V.

According to this, in the cycle of the developing bias T51, the negatively charged toner is overcome by the magnetic force of the magnet 104 by the maximum voltage Vmax (-1320 V) for acceleration of development, and the photosensitive drum 1 from the developing sleeve 102.
00 to both the image part and the non-image part. On the other hand, in the cycle of T52 of the developing bias, the maximum voltage Vmi for pulling back the developing
n (+ 320V) and the magnetic force of the magnet 104
Toner flying on the photosensitive drum 100 in the cycle of T51
It flies to the developing sleeve 102 and is pulled back. At this time, in the image portion on the photosensitive drum 100, the toner having the charge amount corresponding to the development contrast (Vcont) remains in the image portion of the photosensitive drum 100, and the image portion is developed (that is, reverse development).

However, if the reversal toner is present on the developing sleeve 102, the reversal toner flies from the developing sleeve 102 to the non-image portion of the photosensitive drum and adheres thereto in the cycle of T52. This appears as a fog in the white image area on the output image and remarkably deteriorates the image quality (since this fog is due to the reversal toner, it is referred to as "reversal fog" if necessary). This reversal fog contradicts with the fog that occurs in the cycle of T51 due to the negatively charged regular toner (this fog is fog due to the regular toner, so it will be referred to as "regular fog" if necessary), and is reduced overall. Is difficult.

As a countermeasure, it is conceivable to reduce the developing bias AC voltage Vpp shown in FIG.
When p is reduced, the sharpness near the edges of the image tends to be lost, and the image becomes dull. Therefore, a high-quality image cannot be obtained even if the reverse fog is reduced. That is, in order to reduce the total reversal fog, the developing sleeve 1
There is no other way but to charge the toner coated on No. 02 to the specified polarity regularly and uniformly.

To this end, as described above, it is considered to increase the contact pressure of the elastic blade 103 against the developing sleeve 102 so as to promote the triboelectrification of the toner with the surface of the developing sleeve 102. To be However, even if the triboelectrification of the toner with the surface of the developing sleeve can be promoted, the triboelectrification of the toners with each other is also promoted at the same time, and the reversal toner is not significantly reduced.

This is because the contact pressure of the elastic blade 103 to the developing sleeve 102 is always constant and does not change. That is, although the toner near the surface of the developing sleeve 102 has a sufficient charge amount, the contact pressure of the elastic blade 103 is constant, so that the developing sleeve 10 has a constant contact pressure.
(2) The toner cannot move to a place near the surface, and cannot replace the toner having a insufficient amount of charge that is present apart from the surface of the developing sleeve 102. For this reason, the reversal toner does not have a chance to come into contact with the surface of the developing sleeve 102, and it is difficult to obtain a charge amount of regular polarity. As a result, the reversal toner cannot be reduced.

On the other hand, the amount of toner (coating amount) applied to the surface of the developing sleeve 102 is usually 1.0 to 2.0 mg / cm ² and 0.3 mg / c, respectively.
It is considered that the amount of contact with the toner on the surface of the developing sleeve 102 is increased by decreasing to m ² . As a result, the chances of contact between the reverse toner and the surface of the developing sleeve are increased, and the reverse toner can be reduced.

However, since the toner coating amount is reduced, the density of the output image is reduced. To avoid this, the rotation speed of the developing sleeve is set to the photosensitive drum 10.
It is necessary to increase the amount of toner supplied to the developing area to a great extent as compared with the rotation of 0, and as a result, the driving torque of the developing sleeve increases, which causes various problems.

The technique disclosed in Japanese Patent Laid-Open No. 63-52165 has been proposed. This proposed technique aims to reduce the amount of reversal toner and to impart a predetermined charge to the toner. The technique uses a conductive developing blade and 10 ⁶ to 10 ¹² Ωcm.
By using a developing sleeve having a resistance layer on the surface thereof, a voltage is applied to the developing blade to inject an electric charge into the toner to assist the charging of the toner.

However, even in this case, when the layer thickness of the toner applied to the surface of the developing sleeve is large, the injection of electric charges was not sufficiently carried out, and the reversal toner could not be sufficiently reduced. In this case, it may be possible to increase the voltage applied to the developing blade, but if so, the charge amount of the regular toner is given to a predetermined value or more, and the developing efficiency is reduced, so that the toner coating amount is reduced. To
This causes a decrease in image density.

Therefore, it is conceivable to use the proposal of Japanese Patent Laid-Open No. 58-149076 to solve the above problem. In this proposal, in order to regulate the amount of toner on the developing sleeve, instead of the elastic blade, a regulating member made of a conductive rigid body having a contact portion with toner subjected to insulation treatment is used. Then, a voltage having a polarity opposite to the charging polarity of the toner is applied to the regulating member,
An electric field is generated between the developing sleeve and the developing sleeve, and toner is applied to the surface of the developing sleeve by this electric field. As a result, a uniform thin layer coating of toner is obtained,
We are aiming to achieve uniform charging of the toner.

According to the investigations and studies by the present inventors, although not described in the above-mentioned examples of the present invention, redistribution due to the charge polarity of the toner was recognized in the region where the regulating member and the developing sleeve face each other. That is, there is a phenomenon in which the reversal toner is repelled by the positive polarity voltage applied to the regulating member, moves to the surface of the developing sleeve, and the reversal toner is redistributed.

According to this method, the chances of contact of the reversal toner with the surface of the developing sleeve are increased, so that the reversal toner can be made into a regular toner without further thinning the toner coat layer. Therefore, it was expected that the toner could be uniformly charged and the reversal fog could be significantly reduced.

However, as a result of detailed examination, reduction of reversal fog was not sufficiently obtained. One of the reasons is that the regular toner adheres to the vicinity of the regulation portion of the regulation member which is in contact with the toner, cancels the electric field due to the voltage applied to the regulation member, and the redistribution of the toner due to the electric field is not immediately performed. It is to end up. The second reason is that since the gap between the regulating member and the developing sleeve is constant, the pressure generated in the toner coat layer becomes constant, and the toner coat layer becomes in a packing state, and the reversal of the reversal toner is also seen from that surface. It means that distribution will be hindered. The third reason is that since the opposing area between the regulating member and the developing sleeve is narrow, a sufficient nip area for redistributing the reversal toner cannot be obtained, and the redistribution effect does not sufficiently increase. As a result, the reversal toner reduction effect does not increase.

As described above, conventionally, it was very difficult to reduce the amount of reversal toner and obtain a good image without reversal fog.

The object of the present invention is to provide an opportunity for the developer charged to the opposite polarity to the regular charging polarity to come in contact with the surface of the developer carrying member at the contact portion between the developer regulating member and the developer carrying member. It is an object of the present invention to provide a developing device and a process cartridge that can be increased in number and can be normally charged, and can obtain a good image without reversal fog.

[0032]

The above object can be achieved by the developing device according to the present invention. In summary, the present invention includes a developer carrying member carrying a developer, and a developer regulating member which is in contact with the developer carrying body and regulates the developer carried on the developer carrying body. In the developing device, the regulating member is provided on a soft non-conductive elastic member, a conductive layer laminated and supported on the elastic member, and at least a surface of the conductive layer facing the developer carrier. A dielectric layer, and applying a voltage to the conductive layer of the regulating member to regulate the developer charged to the regular charging polarity at the contact portion between the regulating member and the developer carrying member. The developing device is characterized in that an electric field generating means for generating an electric field for applying an attractive force to the surface is generated in a pulsed manner.

According to the present invention, the regulating member may include a soft conductive elastic member and a dielectric layer provided on at least a surface of the elastic member facing the developer carrying member. it can. Further, the surface of the developer carrying member may have a coating layer containing graphite in a resin having a charging polarity opposite to the regular charging polarity of the developer.
Further, these developing devices can be configured as a process cartridge that can be attached to and detached from the main body of the image forming apparatus.

[0034]

【Example】

First Embodiment FIG. 1 is a schematic configuration diagram showing an embodiment of the developing device of the present invention. As shown in FIG. 1, the main developing device 8 includes a developing container 7 containing a toner T which is a one-component developer, and an opening portion of the developing container 7 facing a photosensitive drum (not shown),
A non-magnetic developing sleeve 3 including a fixed magnet roller 5 is rotatably installed, and above the developing sleeve 3, a developing blade 1 is installed as a developer regulating member that is in contact with the rotating direction in the opposite direction. ing.

According to the present invention, the developing blade 1 has the structure shown in FIG.
As shown in FIG. 1, a soft non-conductive elastic member 1a, a conductive layer 1b supported by being laminated on the elastic member 1a, and a conductive layer 1
Dielectric layer 1 provided on the surface of developing sleeve 3 of FIG.
It consists of c and. The developing blade 1 is attached to a developing container 7 by adhering to a conductive blade-shaped rigid body, which is an iron blade 2 in this embodiment. As a result, the developing blade 1
Are in contact with the surface of the developing sleeve 3 with a predetermined pressure.

FIG. 3 shows a side view of the developing blade 1 with the elastic member 1a removed, as viewed from the right side of FIG. As shown in FIG. 3, the conductive layer 1b of the developing blade 1 is brought into contact with the iron blade 2 at the protruding conductive portions 1b 'at both ends in the longitudinal direction to establish electrical conduction.

A soft elastic material is used as the elastic member 1a, but it does not need to be conductive because the developing blade 1 is provided with the conductive layer 1b, and is not conductive.
As the elastic member 1a, for example, urethane rubber or the like can be used. The conductive layer 1b may be basically made of any material as long as it has flexibility and low resistance, but is typically formed using a conductive primer or the like (conductive paint, conductive adhesive, etc.) in which carbon is dispersed. can do. Dielectric layer 1
A material that is flexible, has a high insulating property, and has a high dielectric constant is used for c, and it is preferable to form it in a thin layer. For example, urethane, PFA, PTFE, polyester, polyimide,
Dielectrics such as polyamide can be used. In this embodiment, polyamide 66 (nylon 66) (dielectric constant ε =
4.3, volume resistivity ρ = 10 ¹³ Ωcm) was used to form the dielectric layer 1c with a thickness of 20 μm.

As described above, the developing blade 1 is attached to the developing container 7 by the iron blade 2 and pressed against the developing sleeve 3, and as a result, the nip 4 is formed between the developing blade 1 and the developing sleeve 3. In the nip 4, the toner T is applied on the surface of the developing sleeve 3 in a predetermined coating amount.

In this embodiment, a negative polarity insulating magnetic toner is used as the toner T. For example, an insulating magnetic toner having a volume resistance of about 10 ¹³ Ωcm, which contains 60 wt% of magnetite and 1 wt% of a metal complex salt of a monoazo dye as a negative charge control agent in a binder resin containing styrene-acrylic copolymer as a main component. On the basis of the above, it is possible to use those to which 0.4 wt% of silica fine particles that have been hydrophobized in order to improve fluidity are externally added to the toner weight.

The developing sleeve 3 is made of, for example, aluminum, and the surface of an aluminum pipe processed to have a predetermined outer diameter is sandblasted with Arando A # 400 (Arando abrasive grains) manufactured by Showa Denko KK, and JISB- 0601
The center line average roughness Ra described in (1) can be used.

The magnet rollers 5 included in the developing sleeve 3 are concentrically arranged in the developing sleeve 3 at regular intervals. As shown in FIG. 1, the magnet roller 5 is magnetized by a magnetic pole S1 which is a developing pole, a magnetic pole N2 which is a toner blow-off preventing pole, a magnetic pole S2 which is a toner conveying pole and a magnetic pole N1 which is a toner coating amount regulating pole. Has been formed. In this embodiment, the strength of each magnetic pole is S1 pole: 80
mT, S2 pole: 65mT, N1 pole: 60mT, N2 pole:
It is 70 mT.

The developing sleeve 3 is connected to a superimposed voltage applying means 6 for developing bias, and the iron blade 2 of the developing blade 1 is an electric field generating means 30 for blade bias which is one of the features of the present invention. Are connected.

The superposed voltage applying means 6 comprises a DC power source 10 connected to the developing sleeve 3 and a grounded AC power source 11 connected to the DC power source 10. In this embodiment, the DC voltage of the power source 10 is -500V, the AC voltage of the power source 11 is 1800Hz, and the peak-to-peak voltage is 1640Vp.
p.

The electric field generating means 30 has a DC power supply 12, terminals A and B, and a changeover switch SW. The DC power supply 12 is connected between the DC power supply 10 and the AC power supply 11 of the voltage applying means 6, the terminal B is connected to this DC power supply 12, and the terminal A is connected to the developing sleeve side of the DC power supply 10. The changeover switch SW is connected to the iron blade 2 of the developing blade 1, and the switch SW is provided so that the connection with the terminal A or B can be changed over.

When the changeover switch SW is connected to the terminal A, the superimposed voltage applying means 6 is connected to the iron blade 2 and is applied to the developing sleeve 3 by the DC power supply 10 and the AC power supply 11. The same superposed voltage is applied to the developing blade 1 so that no electric field is generated in the nip 4 between the developing blade 1 and the developing sleeve 3.

On the other hand, when the switch SW is connected to the terminal B, the DC power source 12 of the electric field generating means 30 and the AC power source 11 of the superimposed voltage applying means 6 are connected to the iron blade 2. Since the superimposed voltage by the AC power supply 11 is also applied to the developing sleeve 3, the developing blade 1 and the developing sleeve 3 are
A direct current voltage from the direct current power source 12 and a direct current voltage from the direct current power source 10 form a potential difference in the nip 4, and an electric field is generated in the nip 4 from the developing blade 1 toward the developing sleeve 3.

In this embodiment, the direct current voltage of the direct current power source 12 is set to + 500V, and a potential difference of 1000V is applied between the developing blade 1 and the developing sleeve 3 (-500V) in the nip 4.
It was pulsed at a frequency of 1000 Hz.

The superposed voltage applying means 6 and the electric field generating means 30 are connected to a controller 9 of the main body of the image forming apparatus (not shown), and their operations are controlled by the controller 9. In this embodiment, switching between the terminals A and B by the switch SW is performed at 1000 Hz.

The operation of the developing device of the present invention will be described. When the image forming apparatus (not shown) equipped with the developing device 8 enters the operating state, the controller 9 of FIG.
At the same time that the developing sleeve 3 is rotationally driven, the superimposed voltage applying means 6 and the electric field generating means 30 are driven. As a result, the developing sleeve 3 has a DC of -500V and an AC of 1640V.
A voltage (development bias) in which (1800 Hz) is superimposed is applied, and a direct current of +50 is applied to the conductive layer 1b of the developing blade 1.
A voltage (blade bias) in which AC 1640V (1800Hz) is superimposed on 0V is applied, and as a result, the nip 4
An electric field E having a potential difference of 1000 V from the developing blade 1 toward the developing sleeve 3 is intermittently generated in a pulsed manner at a frequency of 1000 Hz.

Before the nip 4, the toner T on the surface of the developing sleeve 3 is charged with a charge by frictional charging between the toner and the surface of the developing sleeve. However, as described in the conventional example, the toners are charged with each other. By the triboelectric charging, the reversal toner charged with the negative polarity of the regular charging polarity and the positive polarity of the opposite polarity is generated. Therefore, at the position before the nip 4, as shown in FIG. 2, the negatively charged normal toner T1 and the positively charged reversal toner T2 are mixed.

Conventionally, since the electric field E as shown in FIG. 2 is not generated in the nip 4 in a pulsed manner, the toner distribution state in which the reverse toner T2 before the nip 4 is mixed with the regular toner T1 is maintained. Further, the mixed state of the toner distribution is promoted, and the reversal toner T2 increases.

On the other hand, according to the present invention, since the electric field E is applied to the nip 4 in a pulsed manner, the reversal toner T is used.
2 can be reduced. That is, as shown in FIG. 4, which is an enlarged view of the nip 4 in FIG. 2, a force A for attracting the regular toner T1 toward the developing blade 1 in the nip 4 by the electric field E,
A force B that attracts the reverse toner T2 to the surface side of the developing sleeve 3 is generated, and the toners T1 and T2 are redistributed in the nip 4. As a result, the reversal toner T2 moves to the vicinity of the surface of the developing sleeve 3 and the chance of contact with the surface increases, and the toner T2 becomes a normal toner due to the frictional charging.

Other conventional techniques, for example, Japanese Patent Laid-Open No. 58-1
In the case of the technique proposed in 49076, since the electric field E is generated in a constant manner, not in a pulsed manner, once the maximum distribution of the toner T occurs, the regular toner T1 is held on the surface of the developing blade 1, The electric field E is canceled and reduced by the electric charge of the toner T1 itself. Further, since the developing blade is a rigid elastic body and the contact pressure of the developing blade 1 with the developing sleeve 3 is constant in the nip 4, toner is packed between the developing blade and the developing sleeve in the nip. Even if the electric field E is applied, the movement of the toner due to the electric field E is hindered. As a result, even in the above proposal, the redistribution of the reversal toner hardly occurs, and the effect of reducing the reversal toner cannot be maintained.

On the other hand, in the present invention, since the electric field E is turned ON / OFF in a pulsed manner, the electric field E is turned OFF.
Sometimes, the regular toner T1 held on the surface of the developing blade 1
Loses its holding power, is peeled off by the toner coat layer on the developing sleeve 3, and the toner T1 is removed from the surface of the developing blade 1. As a result, when the electric field E is turned on again, there is nothing that obstructs the electric field E, and the maximum distribution of the toner T occurs again in the nip 4.

Further, in the present invention, since the developing blade 1 is provided with the soft elastic member 1a and has the flexible elasticity, the pulse of the electric field E is applied to the developing blade 1 in the nip 4. The contact pressure with the developing sleeve 3 becomes stronger and weaker, and the toner packing state between the developing blade and the developing sleeve is temporarily released, so that the movement of the toner T by the electric field E can be promoted.

From the above, according to the present invention, the reverse toner T
It is possible to increase the chances of contact with the surface of the second developing sleeve 3 and maintain normal toner formation by normal triboelectrification, thereby eliminating reverse toner and obtaining an image free from reverse fog by good development. .

FIG. 5 shows an example in which the developing device of this embodiment is used in an image forming apparatus. When the image forming operation is started, a main motor (not shown) is driven and the photosensitive drum 20 is rotated in the direction of the arrow in the figure. Next, a voltage is applied to the primary charger 21, which charges the surface of the photosensitive drum 20 to a predetermined potential. In this example, the photosensitive drum 20 is -700.
It was charged to V. Then, the exposure device 23 irradiates the laser light 22 to perform image exposure, whereby an electrostatic latent image is formed on the photosensitive drum 20. The latent image on the photosensitive drum 20 is developed by the developing device 8 and visualized as a toner image.

In the developing device 8, simultaneously with the rotation of the developing sleeve 3, the voltage is applied to the developing sleeve 3 and the developing blade 1 as described above. As a result, at the nip 4 between the developing blade 1 and the developing sleeve 3, the developing blade 1
An electric field directed to the developing sleeve 3 is generated in a pulsed manner from the toner, the toner T on the surface of the developing sleeve 3 is favorably charged, the reverse toner is reduced, and the toner T is given a predetermined negative charge. . The toner T negatively charged in this manner is held by the magnetic force on the surface of the developing sleeve 3 and is conveyed to a region facing the photosensitive drum 20,
Therefore, the electrostatic latent image on the surface of the photosensitive drum 20 is reversely developed by the developing bias applied to the area where the photosensitive drum 20 and the developing sleeve 3 face each other.

At this time, in the present invention, the negative charge of the toner T is favorably performed, and the reversal toner is remarkably reduced, so that the reversal toner is less attached to the non-image area of the photosensitive drum 20, A toner image free from reverse fog is obtained.

This toner image is transferred onto the transfer material P conveyed to the photosensitive drum 20 by the registration roller 24, and the transfer material P is sent to the fixing device 27 by the conveyor belt 26, where the toner image is heated and pressed. Being fixed
The image is output. Thus, an image free from reversal fog is obtained.

In the above image formation, the environmental temperature is 10 ° C.
When it was carried out at 33 ° C. and the relative humidity was changed in the range of 10% RH to 90% RH, a good image free from reversal fog was obtained under all environments. As is apparent from the above, as in the present invention, in the nip 4, which is the contact portion of the developing sleeve 3 of the developing blade 1, a pulsed electric field that exerts a force for pressing the reversal toner on the surface of the developing sleeve is generated. As a result, it is possible to stably obtain a good image without reverse fog in all environments.

Embodiment 2 FIG. 6 is an explanatory view showing the vicinity of a developing blade in another embodiment of the developing device of the present invention. In this embodiment, FIG.
5 is characterized in that the terminal B of the electric field generating means 30 is not provided with the DC power supply 12 and the terminal B is grounded.

Therefore, when the changeover switch SW is connected to the terminal A, as in the case of the first embodiment, the superimposed voltage applying means 6 is connected to the iron blade 2, and the DC power source 10 and the AC power source 11 are used to develop the image. The same superposed voltage as that applied to the sleeve 3 is applied to the developing blade 1, and no electric field is generated in the nip 4 between the developing blade 1 and the developing sleeve 3.

On the other hand, when the switch SW is connected to the terminal B, the iron blade 2 is grounded. The contact between the terminal A and the terminal B is switched by the switch SW at 1800 Hz which is the same as the AC component of the developing bias.
When the maximum voltage for acceleration of development (Vmax; see FIG. 12) is applied to the terminal B, it is connected to the terminal B. This makes it possible to generate a pulsed electric field from the developing blade 1 to the developing sleeve 3 without providing the DC voltage 12.

Therefore, also in this embodiment, the chance of friction of the reversal toner with the developing sleeve 3 is increased, the reversal toner is normally charged, and the reversal toner can be significantly reduced, and the surface of the developing sleeve 3 is uniformly charged to a predetermined polarity. By obtaining a toner and developing, a good image free from reversal fog can be obtained. Further, according to the present embodiment, the DC power supply 12 is unnecessary for the electric field generating means 30, so that there is an advantage that the cost is reduced accordingly.

In this example, as in the case of Example 1, the developing device was used in the image forming apparatus shown in FIG. 5 to form an image. As a result, similarly, a good image free from reversal fog could be obtained under all environments.

Embodiment 3 FIG. 7 is an explanatory view showing the vicinity of a developing blade in still another embodiment of the developing device of the present invention. The present embodiment is different in that the terminal A of the electric field generating means 30 of the second embodiment is not connected to the superimposed voltage applying means 6 and the terminal A is floated.

In the first and second embodiments, the changeover switch SW
The conductive layer 1b of the developing blade 1 is connected to the terminal A of the developing blade 1.
The same voltage as that of the developing sleeve 3 was applied to the nip 4 so as not to generate an electric field in the nip 4, but in the present embodiment,
When the changeover switch SW is connected to the terminal A, the iron blade 2 is in a floating state. Since the gap in the contact area between the developing blade 1 and the developing sleeve 3 is very small, the conductive layer 1b of the developing blade 1 has almost the same potential as the developing sleeve 3. That is, it is almost the same as the state in which the switch SW is connected to the terminal A in the first and second embodiments. As a result, in the nip 4, the potential is almost the same as the surface of the developing sleeve 3, and the electric field E exerting a force on the toner T applied on the surface of the developing sleeve 3 is hardly generated.

On the other hand, when the switch SW is connected to the terminal B, the iron blade 2 is grounded, and the contact switching from the terminal A to the terminal B by the switch SW is performed by the developing bias as in the second embodiment. 1800 Hz same as AC component
The maximum voltage (Vma
When x) is applied, it is connected to the terminal B. Accordingly, the electric field from the developing blade 1 to the developing sleeve 3 can be similarly generated in a pulse manner without providing the DC voltage 12.

Also in this embodiment, the chance of friction of the reverse toner with the developing sleeve 3 is increased, the reverse toner can be made to be a regular charge, and can be greatly reduced, and the toner uniformly charged to a predetermined polarity on the surface of the developing sleeve 3. After development, a good image free from reversal fog can be obtained by development. Further, according to the present embodiment, the DC power supply 12 is unnecessary for the electric field generating means 30, so that the cost is reduced accordingly.

In this embodiment, as in Embodiments 1 and 2, the developing device is used in the image forming apparatus shown in FIG.
Image formation was performed. As a result, similarly, a good image free from reversal fog could be obtained under all environments.

Fourth Embodiment In the first to third embodiments, the developing blade 1 has the soft non-conductive elastic member 1a, the conductive layer 1b laminated thereon, and the conductive layer 1b on the surface facing the developing sleeve 3. It has a three-layer structure of the provided dielectric layer 1c.

In this embodiment, the soft non-conductive elastic member 1 is used.
As shown in FIG. 8, instead of a and the conductive layer 1b thereon, one soft conductive elastic member 1d that also serves as the soft conductive elastic member 1d and the developing sleeve 3 thereof is used. The feature is that it has a two-layer structure of the dielectric layer 1c provided on the facing surface.

As the material of the soft conductive elastic member 1d, for example, carbon-dispersed urethane rubber or the like can be used. The elastic member 1d is in direct contact with the iron blade 2 that attaches the developing blade 1 to the developing container 7.

The superposed voltage generating means 6 and the electric field generating means 30 in this embodiment are constructed in the same manner as in the first embodiment, and the connection with these developing blades 1 can be switched by the changeover switch of the electric field generating means 30. did.

Also in this embodiment, the effect of reducing the reversal fog was obtained as in the first embodiment. In this embodiment, since the elastic blade 1 has a two-layer structure, there is an advantage that the elastic blade 1 can be manufactured at a lower cost than in the first embodiment.

Fifth Embodiment In the first to fourth embodiments, a sandblasted product of an aluminum pipe is used as the developing sleeve 3, but in the present embodiment, the developing sleeve 3 is charged with the toner T on the surface of the aluminum pipe. The structure is characterized in that a conductive layer in which graphite particles are dispersed in a resin having a polarity opposite to the polarity (phenol resin in this example) is formed to a thickness of 8 to 22 μm.

Since the above graphite does not form an oxide film like a general metal on the surface, it has a low contact resistance and has a cleavable crystal plane, and therefore has excellent releasability. When the conductive layer containing graphite as a main component is formed on the surface layer of the developing sleeve 3, the developing sleeve 3 is resistant to contamination by ultrafine powder of the resin component in the toner and external additives. Therefore, in the present embodiment, the above-described reverse toner T
The frictional electrification with the surface of the developing sleeve 3 of 2 is further promoted, the reversal toner is more properly charged normally, the reversal toner is remarkably reduced, and the effect of the present invention is further improved.

Sixth Embodiment FIG. 9 is a schematic constitutional view showing still another embodiment of the developing device of the present invention. In this embodiment, the developing device of the present invention is applied to a process cartridge.

The process cartridge 32 is integrally provided with the photosensitive drum 20, the primary charger 21, the developing device 8 and the cleaner 28, and is detachably provided in the main body of the image forming apparatus. The illustrated exposure device 23, registration roller 24, transfer device 25, transport device 26, and fixing device 27 are provided on the image forming apparatus main body side.

By thus constructing the developing device 8 with the photosensitive drum 20 and the like and the process cartridge, not only the maintenance becomes easy, but also the effect of the present invention can be easily exhibited without burdening the user. It will be possible.

[0082]

As described above, in the developing device of the present invention, the regulating member that comes into contact with the developer carrying member to regulate the developer carried thereon is a soft non-conductive elastic member.
A conductive layer laminated and supported on the elastic member, and a dielectric layer provided on at least a surface of the conductive layer facing the developer carrier, or at least a developer of a soft conductive elastic member. A structure comprising a carrier and a dielectric layer provided on the surface facing the carrier, and an electric field generating means are installed,
Applying a voltage to the conductive layer or conductive elastic member of the regulating member,
At the contact portion between the regulation member and the developer carrying member, since an electric field that causes a force to attract the developer charged to the regular charging polarity to the surface of the developer regulation member is generated in a pulsed manner,
It is possible to increase the chances of contact of the developer charged to the opposite polarity with the surface of the developer carrying member, to reduce the developer charged to the opposite polarity by being charged normally, and to obtain a good image without reversal fog. Obtainable.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a developing device of the present invention.

FIG. 2 is an enlarged view showing the vicinity of a developing blade provided in the developing device of FIG.

FIG. 3 is a side view of the developing blade of FIG.

FIG. 4 is an explanatory diagram showing a movement of toner at a contact portion of the developing blade of FIG. 2 with a developing sleeve.

5 is a schematic configuration diagram showing an image forming apparatus using the developing device of FIG.

FIG. 6 is a schematic configuration diagram showing another embodiment of the developing device of the invention.

FIG. 7 is a schematic configuration diagram showing still another embodiment of the developing device of the present invention.

FIG. 8 is an enlarged view showing the vicinity of a developing blade in still another embodiment of the developing device of the present invention.

FIG. 9 is a schematic configuration diagram showing a process cartridge to which the developing device of the present invention is applied.

FIG. 10 is a schematic configuration diagram showing a conventional image forming apparatus.

11 is a configuration diagram showing a main part of a developing device provided in the image forming apparatus of FIG.

FIG. 12 is a diagram showing a potential relationship between a photosensitive drum and a developing sleeve at a conventional image forming position.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Developing blade 1a Non-conductive elastic member 1b Conductive layer 1c Dielectric layer 1d Conductive elastic member 2 Iron blade 3 Developing sleeve 4 Nip 6 Superposed voltage generating means 20 Photosensitive drum 30 Electric field generating means 32 Process cartridge E Electric field T toner

Front Page Continuation (72) Inventor Kenya Ogawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (9)

[Claims] 1. A development comprising: a developer carrying member carrying a developer; and a developer regulating member which is in contact with the developer carrying member and regulates the developer carried on the developer carrying body. In the apparatus, the regulation member includes a soft non-conductive elastic member, a conductive layer laminated and supported on the elastic member, and a dielectric provided on at least a surface of the conductive layer facing the developer carrier. And a voltage is applied to the conductive layer of the regulation member, and the developer charged to the regular charging polarity is applied to the regulation member surface at the contact portion between the regulation member and the developer carrying member. A developing device, wherein an electric field generating means for generating a pulsed electric field for applying an attractive force is installed. 2. The developing device according to claim 1, wherein the electric field generating means comprises a voltage applying means for applying a voltage having a polarity opposite to the charging polarity of the developer in a pulsed manner to the conductive layer of the regulating member. 3. The developing device according to claim 1, wherein the electric field generating means comprises grounding means for grounding the conductive layer of the regulating member in a pulsed manner. 4. The developing device according to claim 1, 2 or 3, wherein a coating layer containing graphite on a resin having a charging polarity opposite to the regular charging polarity of the developer is provided on the surface of the developer carrier. 5. A developing device, comprising: a developer carrying member carrying a developer; and a developer regulating member which is in contact with the developer carrying member and regulates the developer carried on the developer carrying body. In the apparatus, the regulating member includes a soft conductive elastic member and a dielectric layer provided on at least a surface of the elastic member facing the developer carrier, and the elastic member of the regulating member is provided with a voltage. An electric field generating means for generating a pulsed electric field that exerts a force that attracts the developer charged to the regular charging polarity to the surface of the regulation member at the contact portion between the regulation member and the developer carrying member. A developing device that is installed. 6. The developing device according to claim 5, wherein the electric field generating means comprises a voltage applying means for applying a voltage having a polarity opposite to the charging polarity of the developer in a pulsed manner to the conductive layer of the regulating member. 7. The developing device according to claim 5, wherein the electric field generating means comprises grounding means for grounding the conductive layer of the regulating member in a pulsed manner. 8. The developing device according to claim 5, wherein the surface of the developer carrier has a coating layer containing graphite in a resin having a charging polarity opposite to the regular charging polarity of the developer. 9. A process cartridge which includes at least a developing device and is detachable from the main body of an image forming apparatus, wherein the developing device is a developing cartridge.
Or a developing device of 8.