JP2001305876A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of producing high quality flawless image by preventing any scrubbed scratch on a photoreceptor body caused by magnetic particles attaching to a belt shaped body holding a record material, even when a magnetic brush charger employing magnetic particles is used for charging the photoreceptor body. SOLUTION: A fur brush 81 with a magnet 80 at the center forming a toner particle cleaning assembly is in contact with surface of a transfer belt 71 at an upstream position from a cleaning blade 5 removing toner along the rotation direction of the transfer belt 71, so that magnetic particles being carried from the magnetic brush charger 2 to the belt 71 via a photoreceptor drum 3 and attaching on the surface of the belt 71 are scrubbed by the fur brush 81 and caught by the magnet 80.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing method for developing an electrostatic latent image formed on an image carrier corresponding to an image to be recorded with a developer, to visualize the image, and to apply the visible image to a recording material such as paper. The present invention relates to an image forming apparatus that transfers and records an image on a recording material.

[0002]

2. Description of the Related Art Recently, a multifunction peripheral having all output terminals such as a copying machine, a printer, and a fax has been emerging. As such a network-compatible output terminal,
Electrophotographic systems have become widely accepted.

[0003] One of the major problems is the duty cycle of the main body, which is the limit number of sheets that can be operated normally without a service person. The life of the photosensitive drum is one of the largest factors governing the duty cycle.

[0004] In order to eliminate waste from an ecological point of view, reducing the number of consumables, extending the life of components, and increasing reliability have become strong issues for image forming apparatuses. Digitization has progressed from conventional analog devices, and it has become an issue to reduce the main body cost to be equal to or less than that of analog devices.

[0005] In the past, copiers and printers were mainly black-and-white machines, but recently, in offices, the use of full-color originals and output files has been rapidly increasing. For this reason, a full-color printer equivalent to an analog machine and having a main unit cost and a running cost equivalent to a monochrome machine is expected, and it is possible to dramatically reduce the TCO (total required cost as viewed from a user). Technology development is desired.

Under these circumstances, recently, a plurality of photosensitive drums (drum-type photosensitive members) and a belt-shaped recording material carrier for carrying and transporting the recording material, that is, a transfer belt, are provided. For example, a quadruple tandem type color image forming apparatus that obtains a color image on a recording material by sequentially superposing and transferring toner images of different colors formed on respective photosensitive drums onto the material is becoming mainstream. .

In the image forming apparatus, the toner scattered from the photosensitive drum adheres to the transfer belt, the toner is transferred from the photosensitive drum to the transfer belt at the time of a paper jam or a paper gap, or the first surface of the recording material is damaged. When the image is formed on the second surface of the recording material after the toner image transferred to the recording material is fixed, the release agent oil adhered to the recording material during the fixing of the first surface may adhere to the transfer belt. It has been proposed to provide a fur brush type belt cleaning means and to provide an oil cleaner roller or an oil cleaner web for removing the release agent oil from the transfer belt.

On the other hand, although the miniaturization of the electrophotographic image forming apparatus has been promoted, there has been a limit to the miniaturization of each of the steps of charging, exposure, development, transfer, fixing and cleaning.
Further, the transfer residual toner on the photoreceptor is collected as waste toner by a drum cleaner, but it is preferable that the waste toner is not generated from the viewpoint of environmental protection.

For this reason, a cleaner-less device has been developed in which a drum cleaner is eliminated by a simultaneous-development cleaning system in which the transfer residual toner is cleaned simultaneously with development by a developing device. The simultaneous development cleaning is a method in which a small amount of toner remaining on the photosensitive drum after transfer is collected by a fogging bias at the time of development after the next step.

In order to improve the cleaning efficiency by the simultaneous development cleaning method, it is very effective to use a toner having excellent releasability, such as a toner produced by a polymerization method.

[0011] According to the simultaneous development cleaning method, the transfer residual toner can be collected in the developing device and used in the subsequent steps, so that the generation of waste toner is eliminated, and the trouble of maintenance is reduced. it can. In addition, the advantage in terms of space is great, and the image forming apparatus can be significantly reduced in size.

As a charging device for a photosensitive drum, a contact charging device for charging a photosensitive drum by contacting a charging member to which a voltage is applied has been put into practical use because of its advantages such as low ozone and low power consumption. I have. As the charging member, a conductive brush formed of conductive fibers in a brush shape (fur brush) or a conductive rubber roller formed of conductive rubber in a roller shape is preferably used. A magnetic brush system using conductive magnetic particles is preferably used. It is particularly preferable from the viewpoint of charging stability.

The magnetic brush charger forms a magnetic brush by magnetically restraining conductive magnetic particles directly on a magnet or on a support sleeve containing a magnet, and stops or rotates the magnetic brush. The photosensitive member is charged by a voltage applied to the magnetic brush by contacting the photosensitive member.

When a magnetic member is used as a charging member and a photosensitive member having a surface layer in which conductive fine particles are dispersed on an ordinary organic photosensitive member or an amorphous photosensitive member is combined as a member to be charged, the photosensitive member is charged. It is possible to obtain on the surface of the photoreceptor a charging potential substantially equal to the DC component of the voltage applied to the magnetic brush.

Such a charging method is called injection charging. According to this injection charging, since a discharge phenomenon such as a corona charger is not used for charging a photosensitive member, complete ozone-less and low power consumption type charging is achieved. Yes, it is getting attention.

[0016]

By the way, in an image forming apparatus using the above-mentioned contact charging system, when image formation is repeated, toner particles of a developer often mix with the charging member or adhere to the surface. .

Normally, toner having a relatively high electric resistance is used. Therefore, if toner particles are mixed into the charging member or adhere to the surface and become contaminated, the resistance of the whole or a part of the charging member is reduced. And the photosensitive member cannot be charged to a desired potential, or charging unevenness occurs, resulting in an image defect.

This problem is particularly remarkable in a so-called cleaner-less system that does not have a cleaning device for removing transfer residual toner from the photosensitive member, because a large amount of transfer residual toner is mixed into the charging member.

Further, since the transfer residual toner remains on the photoreceptor in the form of an image corresponding to the previous image, if it passes through the contact charger as it is, the remaining portion of the transfer residual toner is charged for the next image formation. A phenomenon in which the potential drops or the exposure is cut off, affecting the development process of the next image formation as it is, and the previous image part becomes thinner or conversely darker on the obtained image (Ghost phenomenon)
Occurs.

Therefore, it has been proposed to uniformly disperse the transfer residual toner on the photoreceptor by using a brush-like uniformizing member or a simple cleaning member utilizing a temporary bias effect. ing.

The transfer residual toner is once collected by the charger by optimizing the contact condition of the charging member with the photoconductor and the charging sequence, and then discharged to the photoconductor by the potential action, and collected by the developing device. A developer reuse system that can be used has been considered.

However, in the case of a magnetic brush charger,
Some of the conductive magnetic particles used reach the transfer section,
The photoreceptor surface deteriorated at the transfer portion, and the magnetic particles that reached the transfer portion also migrated to the transfer belt, slipped through the toner cleaning member such as a counter blade, fur brush or web on the transfer belt, and further slipped. It has been newly found that magnetic particles degrade the photoreceptor surface of other image forming stations.

An object of the present invention is to prevent the photosensitive member from being rubbed by the magnetic particles attached to the belt-shaped recording material carrier even if a magnetic brush charger made of magnetic particles is used for charging the photosensitive member. It is an object of the present invention to provide an image forming apparatus capable of obtaining a good image free from defects.

[0024]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
The surface of the photoreceptor having the charge injection layer is charged by a magnetic brush charger using magnetic particles, and the toner image obtained by image exposure on the charged photoreceptor and development by a developer is used as an endless recording material. An image forming apparatus that transfers the recording material onto which the toner image has been transferred by transferring the recording material carried on the carrier, and separates the toner adhered to the surface of the transfer material carrier after separation by a toner cleaning member; Magnetic particle cleaning for magnetically removing magnetic particles attached to the surface of the recording material carrier at a position after separation of the recording material onto which the toner image has been transferred, and on the upstream or downstream side of the toner cleaning member. An image forming apparatus having a member installed.

According to the present invention, the magnetic particle cleaning member is a fur brush having a magnet in contact with the surface of the recording material carrier. Alternatively, it is a magnet plate close to the surface of the recording material carrier. Alternatively, it is a magnet roller in contact with the surface of the recording material carrier. The magnetic particles have an average particle size of 10 to 100 μm and a saturation magnetization of 2
0-250A · m ² / kg, resistance is 10 ² -10 ¹⁰ Ωcm
It is. The developer is a two-component developer obtained by mixing a non-magnetic toner and a magnetic carrier. The non-magnetic toner is a substantially spherical toner produced by a polymerization method, and has an average particle diameter of 6 to 10 μm and a shape factor. SF-1 is 100-140 and S
F-2 is 100 to 120. The toner cleaning member is a blade in contact with the surface of the recording material carrier. Further, a plurality of photoconductors are provided along the recording material carrier, and a plurality of color toner images on the plurality of photoconductors are
The image is transferred by being superimposed on a recording material carried and conveyed on the recording material carrier.

[0026]

Embodiments of the present invention will be described below in more detail with reference to the drawings.

Embodiment 1 FIG. 1 is a sectional view showing an embodiment of the image forming apparatus of the present invention.

In this apparatus, first, second, third, and fourth image forming units Pa, Pb, Pc, and Pd are provided in parallel, and toner images of different colors are charged, exposed, and developed. And a transfer process.

Image forming units Pa, Pb, Pc and Pd
Is provided with a dedicated image carrier, in this example, electrophotographic photosensitive drums 3a, 3b, 3c and 3d, and a belt-shaped recording material carrier, that is, a transfer belt 71 is installed adjacent to each of the photosensitive drums 3a to 3d. Have been. Photosensitive drum 3a,
3b, 3c, 3d, the chargers 2a, 2
b, 2c, 2d, developing devices 1a, 1b, 1c, 1d, toner leveling members 4a, 4b, 4c, 4d are arranged, and a transfer charger (transfer charging blade) is provided inside the transfer belt 71.
6a, 6b, 6c and 6d are arranged.

The toner leveling member 4 (4a to 4d) averages the toner remaining on the photosensitive drum 3 (3a to 3d) after the transfer of the toner image on the photosensitive drum 3 so as to level the charge and exposure. This is to eliminate the influence of the residual toner. In the image forming apparatus, since the toner leveling member 4 is provided for the photosensitive drum 3, a dedicated drum cleaning device is not provided.

A toner image of each color is formed on each of the photosensitive drums 3a to 3d, and the toner images of each color are transferred in a superimposed manner on a recording material P carried and conveyed on a transfer belt 71. The recording material P on which the toner images of the respective colors have been transferred is conveyed to the fixing device 51, where the toner images are fixed by heating and pressing, and then discharged outside the apparatus as recording images.

The image forming process will be further described.
The original G is set on the platen 10 with the surface to be copied facing downward. Next, copying is started by pressing the copy button. A document illumination lamp (not shown), a single-focus lens array, and a CCD sensor are integrated into a single unit, and scanning is performed while irradiating the document. Then, the light is incident on the CCD sensor.

The CCD sensor comprises a light receiving section, a transfer section, and an output section. The light signal is converted into a charge signal in the CCD light receiving section, and is sequentially transferred to the output section in synchronization with the clock pulse in the transfer section. The output section converts the charge signal into a voltage signal, and amplifies and lowers the impedance for output. I do. The analog signal thus obtained is converted into a digital signal by performing known image processing, and sent to a printer unit.

The printer section receives the image signal and forms an electrostatic latent image as follows. Each of the photosensitive drums 3 (3a to 3d) is driven to rotate in a direction indicated by an arrow at a predetermined peripheral speed about a center support shaft, and during the rotation process, the magnetic brush charger 2 (2a to 2) is driven to rotate in the direction indicated by an arrow.
According to d), the surface of the solid-state laser element which is uniformly charged to the negative polarity and which is turned on and off in accordance with an image signal is scanned on the uniformly charged surface by a polygon mirror rotating at a high speed. As a result, an electrostatic latent image corresponding to the document image is sequentially formed on the surface of the photosensitive drum 1.

In the present invention, the photosensitive drum 3 (3a-3)
As d), a commonly used organic photoreceptor or the like can be used. Preferably, a surface layer having a material having a resistance of 10 ⁹ to 10 ¹⁴ Ωcm on the organic photoreceptor, an amorphous silicon photoreceptor, or the like is used. Is effective in preventing generation of ozone and reducing power consumption. In addition, the chargeability can be improved.

Therefore, in this embodiment, the photosensitive drum 3 is formed on an aluminum drum base having a diameter of 30 mm.
A negatively chargeable photosensitive drum made of an organic photoreceptor, in which the following first to fifth layers were provided in order from the bottom, was used.

The first layer is an undercoat layer, which is provided for smoothing out defects or the like of the aluminum substrate, and is a conductive layer having a thickness of 20 μm.

The second layer is a positive charge injection preventing layer, which serves to prevent positive charges injected from the aluminum substrate from canceling negative charges charged on the surface of the photoreceptor, and comprises an amylan resin and methoxymethylated nylon. By 10 ⁶ Ω
It is a medium resistance layer having a thickness of 1 μm and a resistance adjusted to about cm.

The third layer is a charge generation layer, which is a layer having a thickness of about 0.3 μm in which a disazo pigment is dispersed in a resin, and generates positive and negative charge pairs upon exposure.

The fourth layer is a charge transport layer, and is made of a P-type semiconductor in which hydrazone is dispersed in a polycarbonate resin.
Therefore, negative charges charged on the surface of the photoreceptor cannot move through this layer, and only positive charges generated in the charge generation layer can be transported to the surface of the photoreceptor.

The fifth layer is a charge injection layer, which is a coating layer of a material in which ultrafine SnO ₂ particles are dispersed as conductive fine particles in a binder of an insulating resin. Specifically, a coating liquid in which 70% by weight of ultra-fine SnO ₂ fine particles having a particle size of 0.03 μm, which has been reduced in resistance (conducted) by doping antimony which is a light-transmitting conductive filler, is dispersed in an insulating resin is used. It was prepared and applied to a thickness of 3 μm by a suitable coating method such as dipping coating method, spray coating method, roll coating method, and beam coating method to form a charge injection layer.

In this embodiment, the charger 2 (2a to 2d) is of a magnetic brush charging type. In this embodiment,
As shown in FIG. 2, the magnetic brush charger 2 has a sleeve rotating type magnetic brush charging member 31 installed in a container 30. The charging member 31 has a fixed S pole and two N poles. A magnet roller 32, a non-magnetic sleeve 33 having an outer diameter of 16 mm rotatably fitted to the outside of the magnet roller, and a magnetic brush 34 of magnetic particles held on the surface of the sleeve by the magnetic force of the magnet roller
Consists of

At the opening of the container 30 on the photosensitive drum 1 side,
A regulating blade 35 for regulating the layer thickness of the magnetic brush 34 on the sleeve 33 is attached at a position on the upstream side in the rotation direction of the sleeve 33, and the toner leveling member 4 is attached on a position on the downstream side in the rotation direction of the sleeve 33. Has been
The leveling member 4 is made of a brush and also serves as a sealing member for magnetic particles. The sleeve 33 is connected to a high-voltage power supply 37 for applying a charging bias.

In the present embodiment, the sleeve 33 rotates in the counter direction with respect to the photosensitive drum 1, and the sleeve 33 rotates at a speed of 100 mm / sec.
Rotated at m / s. The photosensitive drum 1 of the magnetic brush 34
The width of the contact nip was adjusted to approximately 6 mm. Sleeve 33
There is a tendency that the higher the rotation speed, the better the uniformity of charging.

The charger 2 rotates in the counter direction by the rotation of the sleeve while the magnetic brush 34 on the sleeve 33 is in contact with the surface of the photosensitive drum 1, so that the DC voltage and the AC voltage applied to the sleeve 33 from the power source 37. Is charged via the magnetic particles to the surface of the photosensitive drum 1 with the superimposed charging bias, and the surface is charged to a voltage corresponding to a charging voltage (a DC voltage) by an injection charging method.

The magnetic particles constituting the magnetic brush 34 have an average particle diameter of 10 to 100 μm and a saturation magnetization of 20 to 250 e.
mu / cm ³ (A · m ² / kg), resistance is 10 ² to 10 ¹⁰
Ωcm is preferable. Considering that there is an insulation defect such as a pinhole in the photosensitive drum, the resistance is 1 Ωcm.
0 ⁶ Ωcm or more is desirable. As the magnetic particles, those having the smallest possible resistance are preferably used in order to improve the charging performance. In this embodiment, the average particle diameter is 25 μm, the saturation magnetization is 200 emu / cm ³ , and the resistance is 5 × 10 ⁶ Ωcm. Was used.

The measurement of the resistance value of the magnetic particles was performed when the bottom area was 22
After placing 2 g of magnetic particles in an 8 mm ² metal cell, 6.6
With a weight of kg / cm ² , 10
The test was performed by applying a voltage of 0V.

As magnetic particles, a resin carrier formed by dispersing magnetite of a magnetic material in a resin and dispersing carbon black for conductivity and resistance adjustment, or a magnetite simple substance surface such as ferrite is coated with a resin. , For which resistance adjustment is performed.

The frequency of 1000 is applied to the sleeve 33 of the charger 2.
FIG. 5 shows the relationship between the charging potential of the first rotation of the photosensitive drum and the amplitude of the alternating voltage when a charging bias in which an alternating voltage of a rectangular wave of Hz is superimposed is applied.

As is apparent from FIG. 5, by increasing the amplitude (Vpp) of the alternating voltage, the difference between the DC voltage (-700 V) of the charging bias and the charging potential in the first cycle is reduced. More specifically, the DC component of the charging bias is Vdc
And the surface potential of the charged photosensitive drum at this time is Vs
If ΔV = | Vdc−Vs |, which is the difference between them, becomes approximately 40 V or less, the uniformity of charging is improved.

Therefore, in this embodiment, the DC voltage is −700
A charging bias in which a rectangular wave alternating voltage having a frequency of 1000 Hz and an amplitude of 800 V was superimposed on V was applied to the sleeve 33. As a result, the surface of the photosensitive drum 1 is reduced by about -700.
V was uniformly charged.

In this embodiment, the developing units 1 (1a to 1d) are of a two-component magnetic brush developing type. Magnetic brush developer 1
As shown in FIG. 2, a developing sleeve 4 rotatably installed in an opening of the developing container 46 facing the photosensitive drum 3.
1, a magnet roller 46 disposed non-rotatably in the developing sleeve 41, developer stirring screws 43 and 44 disposed in the lower part of the container 46, and a part disposed on the developing sleeve 41 of the container 46. A regulating blade 45 is provided, and a two-component developer is contained in a container 46.

The developing sleeve 41 is arranged so that the area closest to the photosensitive drum 3 is at least about 500 μm at the time of development, and the developer carried on the developing sleeve 41 is in contact with the photosensitive drum 1. Thus, the electrostatic latent image on the photosensitive drum 3 can be developed.

In this embodiment, the toner of the two-component developer is
A negatively charged toner having an average particle diameter of 6 μm manufactured by a pulverization method was used by externally adding 1% by weight of titanium oxide having an average particle diameter of 20 nm. The magnetic carrier of the two-component developer has a saturation magnetization of 205 A · m ² / kg and an average particle diameter of 35 μm.
Was used. The mixing ratio of the toner and the carrier of the developer was 6:94.

The developing step of developing a latent image on the photosensitive drum 3 by the two-component magnetic brush method using the developing device 1 will be described.

First, the two-component developer in the developing container 46 is
With the rotation of the developing sleeve 41, it is pumped up by the magnetic pole N3 of the magnet roller 42, and N3 pole → S2 pole → N1
In the process of being transported with the poles, it is regulated by a regulating blade 45 arranged perpendicular to the developing sleeve 41,
A thin layer is formed on the developing sleeve 41. When the developer formed in the thin layer is transported to the developing main pole S1, the developer is raised by the magnetic force and is formed on the magnetic brush.

Then, the developer formed on the spike-shaped magnetic brush comes into contact with the surface of the photosensitive drum 3, and the toner in the developer adheres to the electrostatic latent image on the photosensitive drum 3 to perform development.
The latent image is visualized as a toner image. After the development, the developer is transferred to the developing container 41 as the developing sleeve 41 rotates.
And is separated from the developing sleeve 41 by the repulsive magnetic field formed by the magnetic poles N2 and N3, and collected in the container 46.

At the time of development, a voltage obtained by superimposing a DC voltage and an AC voltage from a power source (not shown) is applied to the developing sleeve 41. In this embodiment, the DC voltage is -500 V, the AC voltage is Vpp = 1500 V, and Vf = 2000 Hz. And In general, in the two-component development method, when an AC voltage is applied, the development efficiency is increased, and the quality of an image is high. On the contrary, there is a risk that fogging is likely to occur. For this reason, fog is generally prevented by providing a potential difference between the DC voltage applied to the developing sleeve 41 and the surface potential of the photosensitive drum 3.

The toner image formed on the photosensitive drum 3 is
The image is transferred to the recording material P by the transfer device 7. Transfer device 7
Are a transfer belt 71 as a recording material carrier, a transfer charging blade 6 (6a to 6d), and a transfer belt 7
The transfer charging blade 6 includes a driving roller 72, a driven roller 73, and the like.
Abuts against the back surface of the transfer belt 71 at a position opposite to the photosensitive drum 3 to form a transfer portion.

The transfer belt 71 is made of polyimide resin, polycarbonate resin, polyethylene terephthalate resin,
It is made of a sheet of dielectric resin such as polyvinylidene fluoride resin, polyethylene naphthalate resin, polyether ether ketone resin, polyether sulfone resin, polyurethane resin, or a fluorine-based rubber or silicone-based rubber rubber sheet. An endless shape belt which is overlapped and joined, or a seamless (seamless) belt is used. The thickness is approximately 25-2000 μm, preferably 50-150 μm
m is preferred. In this embodiment, the transfer belt 71
Was formed from a polyimide resin sheet having a thickness of 75 μm.

A recording material P is supplied from a recording material cassette (not shown) to a transfer belt 71 via a plurality of conveying rollers and registration rollers 12 in accordance with image formation in each of the image forming units Pa to Pd. It is electrostatically attracted to the transfer belt 71. The recording material P carried on the transfer belt 71 in this manner is sequentially conveyed through each transfer section by the rotation of the transfer belt in the direction of the arrow, and the toner image of each color formed on each photosensitive drum 3 is recorded on the recording material. The transfer is superimposed and transferred onto P by the action of the transfer bias applied to the transfer charging blade 6.

The transfer charging blade 6 has a resistance of 10
⁵ to 10 ⁷ Ω, a thickness of 2 mm, and a length of 306 mm were used. A transfer bias of 15 μA was applied under constant current control.

The recording material P on which the toner images of the four colors have been superimposedly transferred in this manner is neutralized by a separation static eliminator (not shown) downstream of the transfer belt 71 in the transport direction to attenuate the electrostatic attraction force. Is released at the end of the transfer belt 71. The detached recording material P is sent to the fixing device 9.

The fixing device 9 includes a fixing roller 51 and a pressure roller 52 pressed against the fixing roller 51, and further includes a heat-resistant cleaning member for cleaning these rollers, a heater installed in each roller, and the like. . The recording material P to which the four color toner images have been transferred is nipped by a fixing nip portion where the fixing roller 51 and the pressure roller 52 are in contact, and heated and pressed while being conveyed by the rotation of these rollers. The four colors of toner are mixed and fixed to form a full-color fixed image.

In this example, a mixture of a non-magnetic polymerized toner manufactured by a suspension polymerization method and a resin-coated magnetic carrier manufactured by a polymerization method was used as a two-component developer.

The toner concentration (T / D ratio) of this developer is 8
% By weight. The magnetic carrier has a magnetization of 100 emu / cm ³ in a magnetic field of 1 kOe, a number average particle size of 40 μm, and a specific resistance of 10 ¹³ Ωcm.
Was used.

The polymerized toner has a shape factor SF-1 of 115, SF-2 of 110 and a substantially spherical surface with a smooth surface, a weight average particle size of 8 μm, and a specific gravity of 1.05 g / cm ^3.
The toner having an average charge per unit mass of 25 μC / g was used.

In the present invention, a substantially spherical polymer having a shape factor SF-1 in the range of 100 to 140 and SF-2 in the range of 100 to 120 is preferable for maintaining high transfer efficiency.

In the present invention, the shape factors SF-1, SF
-2 is a scanning electron microscope FE- manufactured by Hitachi, Ltd.
Using an SEM (S-800), 100 toner particle images are sampled at random, and the image information is obtained via an interface using an image analyzer (Luzex manufactured by Nicole).
It was introduced in 3), analyzed, and defined as a value calculated from the following equation.

SF-1 = ｛(MXLNG) ² / ARE
A｝ × (π / 4) × 100 SF-2 = {(PERI) ² / AREA)｝ × (1/4
π) × 100 where AREA: toner projection area, MXLNG: absolute maximum length, PERI: peripheral length By using such a spherical toner, transfer efficiency becomes 9
5% or more can always be secured, which is an important factor in building a cleaning system.

In this embodiment, a cleaning blade 5 is provided as a toner cleaning member at a position downstream of the separation portion of the recording material P in the rotation direction of the transfer belt 71, and this is applied to the surface of the transfer belt 71. The toner adhered to the transfer belt 71 during the image formation on the recording material P is wiped off by contact.

The cleaning blade 5 had a rubber hardness of 77 ° (JISA), a rebound resilience of 45% (23 ° C.), a plate thickness of 2 mm, and a free length of 8 mm. The cleaning unit including the cleaning blade 5 has a swing angle of 0 °,
The contact angle was 25 °, and the total contact pressure against the transfer belt 71 was 1.5 kgf (1.5 × 9.80665N).

However, conductive magnetic particles from the magnetic brush charger 2 are adhered to the transfer belt 71 via the photosensitive drum 3 and cannot be satisfactorily removed by the cleaning blade 5. Therefore, in the present invention, the transfer belt 7
A magnetic particle cleaning member is provided upstream or downstream of the cleaning blade 5 in the rotation direction of No. 1 to remove magnetic particles on the surface of the transfer belt 71.

In this embodiment, a fur brush 81 having a magnet 80 at the center is provided as a toner particle cleaning member at a position upstream of the cleaning blade 5, and the fur brush 81 is brought into contact with the transfer belt 71, and The conductive magnetic particles are scraped off by a fur brush 81 and collected by a magnet 80.
Was also neutralized. The magnet 80 has a surface magnetic flux density of 1000
Gauss (100 mT) was used.

In this embodiment, as described above, the photosensitive drum 3
Even when the magnetic brush charger 2 made of magnetic particles is used for charging, the magnetic particles attached to the transfer belt 71 are removed by the fur brush 81 having the magnet 80, so that the photosensitive drum 3 is prevented from being scratched by the magnetic particles. As a result, a good image free from defects such as scratches can be stably obtained.

By the way, according to the present embodiment, as a result of the image output durability test, no large scratches were observed on the photosensitive drum over a long period of 100,000 sheets, and a good image was stably obtained.

Embodiment 2 FIG. 3 is a sectional view showing another embodiment of the image forming apparatus of the present embodiment.

The image forming apparatus of the present embodiment employs the transfer belt 7
At a position downstream of the first cleaning blade 5, a magnet plate 83 as a magnetic particle cleaning member is disposed close to the transfer belt 71, and the magnet plate 83 removes magnetic particles attached to the surface of the transfer belt 71. .

The other structure of the present embodiment is basically the same as that of the first embodiment described with reference to FIGS. 1 and 2. In FIG. 3, the same reference numerals as those shown in FIG. 1 denote the same members.

The magnet plate 83 was produced by binding a rare earth ferromagnetic material of barium ferrite with a thermoplastic resin, preferably a polyamide resin such as nylon-12.
As the rare earth-based ferromagnetic material, strontium ferrite, R-Co-based, and R-Fe-B-based can also be used.

As the binder resin, a flexural modulus (ASTM)
Measured according to D-790. However, the value at the time of drying) is 1
00 kgf / mm ² or more (preferably 150 kgf / m 2
m ² or more) of the polyamide resin, for example nylon-6,
Nylon-66 may be used.

According to this embodiment, even if the magnetic particles from the magnetic brush charger 2 used for charging the photosensitive drum 3 adhere to the transfer belt 71, the magnetic particles are collected and removed by the magnet plate 83. The photosensitive drum 3 made of magnetic particles
No scratches were found on the photosensitive drum over a long period of 100,000 sheets in the image output durability test.
A good image without defects such as scratches could be obtained stably.

Embodiment 3 FIG. 4 is a sectional view showing still another embodiment of the image forming apparatus of the present embodiment and its magnet roller.

In this embodiment, as shown in FIG.
A magnet roller 86 was provided as a magnetic particle cleaning member at a position downstream of the cleaning blade 5 of the transfer belt 71. This magnet roller 86 is similar to that shown in FIG.
As shown in (b), a non-woven fabric 85 was wound to a thickness of 2.0 mm to make the surface soft so that it could be used in contact with the transfer belt 71.

The magnet of the magnet roller is made of a rare earth ferromagnetic material of barium ferrite and nylon-12.
And the like.

In this embodiment, even if the magnetic particles from the magnetic brush charger 2 used for charging the photosensitive drum 3 adhere to the transfer belt 71, the magnetic particles are collected and removed by the magnet roller 86. As a result, as in Examples 1 and 2, no large scratches were observed on the photosensitive drum over a long period of 100,000 sheets in the image-production durability test, as in Examples 1 and 2. As a result, a good image free from defects was obtained stably.

In each of the above embodiments, a case where a color image is formed by providing a plurality of photosensitive members has been described. However, the present invention is not limited to this. This can be applied to the case of forming an image.

[0088]

As described above, according to the present invention,
Even if a magnetic brush charger made of magnetic particles is used to charge the photoconductor, a cleaning member such as a fur brush having a magnet is installed on the belt-shaped recording material carrier, and the magnetic particles adhered to the surface of the recording material carrier. Magnetically removes
The photoreceptor can be prevented from being rubbed and scratched by magnetic particles attached to the surface of the recording material carrier, a good image free from defects such as scratches can be obtained, and the life of the photoreceptor can be improved. In addition, since the photoconductor is charged by combining a magnetic brush charger with a photoconductor having an electric field injection layer on the surface, complete ozone-free and low power consumption charging can be performed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an embodiment of an image forming apparatus according to the present invention.

FIG. 2 is a cross-sectional view showing a magnetic brush charger and a developing device used in the image formation of FIG.

FIG. 3 is a sectional view showing another embodiment of the image forming apparatus of the present invention.

FIG. 4 is a cross-sectional view schematically illustrating another embodiment of the image forming apparatus of the present invention and a magnet roller.

FIG. 5 shows the charging potential and the amplitude of the AC voltage in the first rotation of the photosensitive drum when a charging bias in which a rectangular wave AC voltage having a frequency of 1000 Hz is superimposed is applied to the sleeve of the magnetic brush charger used in the present invention. FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 1a-1d Developing device 2, 2a-2d Magnetic brush charger 3, 3a-3d Photosensitive drum 5 Toner cleaning blade 34 Magnetic brush 71 Transfer belt 80 Far brush 81 Magnet 83 Magnet plate 85 Nonwoven fabric 86 Magnet roller

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 15/01 G03G 9/08 361 15/02 101 384 F-term (Reference) 2H003 BB11 CC04 2H005 AA15 AA21 AB06 CA21 EA05 FA01 2H030 AB02 AD02 AD03 2H032 AA15 BA01 BA18 BA23 BA30 2H068 AA05 CA37 FB13 FC01 FC08 FC15

Claims (8)

[Claims] 1. A surface of a photoreceptor having a charge injection layer is charged by a magnetic brush charger using magnetic particles, and a toner image obtained by image exposure of the charged photoreceptor and development by a developer is obtained. An image which is transferred to a recording material carried on an endless recording material carrier and conveyed, and the recording material on which the toner image has been transferred is separated from the transfer material carrier after the toner image is separated. In the forming apparatus, at a position after separation of the recording material onto which the toner image has been transferred, and upstream or downstream of the toner cleaning member, magnetic particles adhering to the surface of the recording material carrier are magnetically An image forming apparatus comprising a magnetic particle cleaning member to be removed. 2. The image forming apparatus according to claim 1, wherein said magnetic particle cleaning member is a fur brush having a magnet in contact with a surface of said recording material carrier. 3. The image forming apparatus according to claim 1, wherein the magnetic particle cleaning member is a magnet plate close to a surface of the recording material carrier. 4. The image forming apparatus according to claim 1, wherein said magnetic particle cleaning member is a magnet roller in contact with a surface of said recording material carrier. 5. The magnetic particles having an average particle size of 10 to 100.
The image forming apparatus according to claim 1, wherein the saturation magnetization is 20 to 250 emu / cm ³ , and the resistance is 10 ² to 10 ¹⁰ Ωcm. 6. The developer is a two-component developer in which a non-magnetic toner and a magnetic carrier are mixed. The non-magnetic toner is a substantially spherical toner produced by a polymerization method, and has an average particle diameter of 6%. 10 to 10 μm, shape factor SF-1 is 100 to 14
The image forming apparatus according to claim 1, wherein SF-2 is 100 to 120 at 0. 7. 7. The toner cleaning member according to claim 1, wherein the blade is in contact with a surface of the recording material carrier.
7. The image forming apparatus according to any one of items 6. 8. A plurality of photoconductors along the recording material carrier, and a plurality of color toner images on the plurality of photoconductors are
The image forming apparatus according to claim 1, wherein the image is transferred by being superimposed on a recording material carried and conveyed on the recording material carrier.