JPH112940A - Image forming method - Google Patents

Abstract

(57) Abstract: An object of the present invention is to provide a method for forming a good image over a long period of time without being affected by residual toner in a cleanerless system. The present invention relates to a charging step of charging a photosensitive member by applying a voltage to a charging member arranged in contact with an electrophotographic photosensitive member, a latent image forming step, and an obtained electrostatic latent image is formed by toner. An image forming method comprising: a developing step of reversal developing; and a transferring step of transferring the obtained toner image to a transfer material, and collecting the toner remaining on the photoreceptor after the transferring step by the developing step. The polarity of the potential generated on the photoconductor due to the rubbing of the photoconductor is opposite to the polarity of the potential for charging the photoconductor during image formation, and the toner is rubbed against the charging member. Wherein the polarity of the charge generated in the toner is the same as the polarity of the potential for charging the photosensitive member during image formation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using a contact charging member, a photoreceptor and a toner.
By charging the photoreceptor having the charge injection layer by applying a voltage from the contact charging member, by controlling the chargeability of the transfer residual toner passing through the charge to one suitable for collection in development. The present invention is applied to an electrophotographic apparatus such as a printer, a copying machine, and a facsimile which does not require an independent cleaning device.

[0002]

2. Description of the Related Art Conventionally, a number of methods are known as electrophotography. In general, a photoconductor using a photoconductive material is uniformly charged and an electric latent image is formed by image exposure. Then, the latent image is developed with a toner to form a visible image,
If necessary, a toner image is transferred onto a transfer material such as paper, and then the toner image is fixed on the transfer material by heat, pressure or the like to obtain a copy or print. Further, toner particles remaining on the photoconductor without being transferred onto the transfer material are removed from the photoconductor by a cleaning process.

For this cleaning step, conventionally, blade cleaning, fur brush cleaning, roller cleaning and the like have been used. In either method, the toner remaining after transfer is mechanically scraped off or dammed and collected in a waste toner container. Therefore, there has been a problem that such a member is pressed against the surface of the photoconductor. For example, pressing the member strongly wears the photoconductor and shortens the life of the photoconductor.

[0004] From the viewpoint of the apparatus, the provision of such a cleaning apparatus inevitably increases the size of the apparatus, which has been a bottleneck when aiming for a more compact apparatus.

Further, from the viewpoint of ecology, there has been a demand for a system which does not generate waste toner in terms of effective utilization of toner.

As one of the image forming methods using an electrophotographic method when such a cleaning device is not required, a method of simultaneously performing development and cleaning of untransferred residual toner which has not been transferred during a developing process, a so-called cleanerless system. There is a technology called.

Also, in the method of charging by contacting the photoreceptor and the transfer in contact with the photoreceptor via a transfer material, contact transfer generally generates less ozone from the viewpoint of ecology. Is a desirable configuration. The transfer member also serves as a transfer material transport member, and has a feature that the size of the apparatus is easily reduced.

[0008]

However, since charging and transfer are performed by contacting the photoreceptor, in the above-described cleanerless system, the transfer residual toner directly stains the contact charging member as it is. In addition, although there is no problem with the initial image, there is a problem that the image is easily stained due to poor charging of the photosensitive member due to durability.

Further, if the cleaning in the developing section is insufficient, the transfer member and the charging member are easily stained, and image stains due to poor charging of the photoreceptor, back stain on the transfer material, or the transfer rate or the central portion of the line portion are reduced. There is a problem in that untransferred untransferred portions tend to occur, which further accelerates image deterioration.

It is an object of the present invention to provide a method for forming a good image over a long period of time without being affected by residual toner in a cleanerless system. Specifically, by suppressing the amount of transfer residual toner mixed into the contact charging member, contamination of the charging member by the transfer material toner is prevented, and the polarity of the transfer residual toner is maintained during the developing process. Accordingly, it is an object of the present invention to provide an image forming method that improves the recoverability of the transfer residual toner in the developing process.

[0011]

That is, the present invention provides a charging step of charging a photosensitive member by applying a voltage to a charging member arranged in contact with the electrophotographic photosensitive member, and exposing the charged photosensitive member. A latent image forming step of forming an electrostatic latent image on the photoreceptor, a developing step of reversal developing the obtained electrostatic latent image with toner, and a transfer step of transferring the obtained toner image to a transfer material. In the image forming method for recovering the toner remaining on the photoreceptor after the transfer step in the developing step, the polarity of the potential generated on the photoreceptor due to the rubbing of the charging member and the photoreceptor is changed. Sometimes, the polarity of the potential that charges the photoconductor is opposite to the polarity of the potential that charges the photoconductor, and the polarity of the charge that is generated in the toner due to the toner rubbing against the charging member is the potential of the potential that charges the photoconductor during image formation. Polarity and same polarity The image forming method characterized in that it.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

First, the principle of the simultaneous development cleaning method, that is, the cleanerless image forming method will be described.

The principle is to control the charge polarity and the charge amount of the toner on the photoreceptor in each step of electrophotography and to use the reversal development method.

For example, in the case of reversal development using a negatively charged photosensitive member and a negatively charged toner, in the transfer step, a toner image visualized by a positive polarity transfer member is transferred to a transfer material. To be transferred, the type of transfer material (difference in thickness, resistance, dielectric constant, etc.)
And the image area and the like, the charging polarity of the transfer residual toner varies from plus to minus. However, even if the transfer residual toner along with the photoreceptor surface oscillates in the positive polarity during the transfer process, the negatively charged photoreceptor charges the negatively charged photoreceptor so that the negatively-charged charging member is uniformly applied to the negative side. The charging polarity must be uniform. When the reversal development is used as the developing method, the negatively charged transfer residual toner remains as it is in the bright portion potential portion of the toner to be developed, and the dark portion potential of the toner should not be developed. Means that the toner remaining after transfer is attracted to the toner carrier due to the development electric field,
No toner remains on the photoreceptor having a light portion potential.

As described above, by making the charge polarity of the transfer residual toner the same as the polarity of the charge held by the toner in the developing process, simultaneous development cleaning (cleanerless) is performed.
An image forming method is established.

Further, since the transfer residual toner is in direct contact with the charging member, the charging member is easily contaminated. In particular, the charging member is contaminated by accumulation of the transfer residual toner on the surface and inside of the charging member, and poor charging occurs. Therefore, the contact charging member sets the charge of the transfer material toner to the polarity opposite to the polarity of the potential placed on the photoconductor at the time of image formation, and returns the toner having the same polarity to the photoconductor so as not to accumulate in the charger. There must be.

What is important in the present invention is a step of adjusting the charge of the toner remaining after transfer to a polarity opposite to the polarity of the potential placed on the photosensitive member at the time of image formation by a contact charging member, and returning the toner to the photosensitive member. Yes, if the charge of the transfer residual toner cannot be sufficiently controlled and passes through the charger as it is, the length of one round of the photoconductor is shorter than the length of the transfer material in the traveling direction due to light shielding by the transfer residual toner. If
Since the charge exposure and development must be performed in the state where the transfer residual toner is present on the photoconductor, the potential on the surface of the photoconductor where the transfer residual toner is present cannot be sufficiently reduced and the development contrast becomes insufficient. Appears on the image as a negative ghost with a lower density than the surroundings, or
Since the cleaning effect of the transfer residual toner is insufficient at the time of development, the toner is developed on the surface of the photoreceptor where the transfer residual toner is present, so that the density is higher than the surrounding area, and a positive ghost occurs. Further, even if the image pattern is scattered by the charger, the image pattern cannot be collected in the developing step, so that an image defect called a fog image occurs.

In order to prevent the above image defects, it is possible to maintain sufficient contact with the photoreceptor, perform sufficient rubbing with the untransferred toner, and prevent various toners. From the viewpoint that control is possible by easily selecting a resin that coats the triboelectric charge polarity, the form of the contact charging member is preferably magnetic particles, and the applied voltage is an AC superimposed voltage during image formation and a non-image It is preferable to apply a DC voltage having the same polarity during image formation as during image formation.

As the AC component, in the case of the injection charging method,
100Hz to 10k depending on the process speed of the equipment
At a frequency of about Hz, the peak-to-peak voltage of the applied AC component is preferably about 1000 V or less. If the voltage exceeds 1000 V, a potential of the photosensitive member is obtained with respect to the applied voltage, so that the latent image surface may be waved in potential, causing fogging and density fading.

In the case of the charging method using electric discharge, the AC component is 100 Hz depending on the process speed of the apparatus.
At a frequency of about 10 kHz to about 10 kHz, the peak-to-peak voltage of the applied AC component is about 1000 V or more, and the discharge starting voltage is 2
More than twice is preferred. As the waveform of the applied AC component, a sine wave, a rectangular wave, a sawtooth wave, or the like can be used.

From the viewpoint of the probability of contact between the transfer residual toner and the charging member, a brush-shaped charging member is more advantageous in terms of a contact surface area than a surface-shaped charging member (such as a rubber roller). Minutes, it is easy to align the polarity of the transfer residual toner,
In the case of a rubber roller or the like, since it is impossible to temporarily transfer the transfer residual toner to the charging member, it is difficult to make the polarity of the transfer residual toner uniform. Therefore, a brush-like charging member is used as the charging member. preferable.

When a magnetic brush using magnetic particles is used as a charging member and an AC superimposed voltage is applied, the transfer residual toner is easily and easily taken into the magnetic brush by the effect of the oscillating electric field of the applied voltage. Thereby, generation of the ghost image as described above can be prevented.

Further, once taken into the charger, the transfer residual toner can sufficiently rub against the magnetic particles, and the polarity of the transfer residual toner is set to a polarity opposite to that of the charged potential placed on the photosensitive member. It is possible to make them fully aligned.

However, if the AC voltage is continuously applied, the transfer residual toner is accumulated in the charger, and the charger is gradually contaminated, resulting in an image defect due to a charging failure. Therefore, during non-image formation (during pre-rotation, post-rotation, at the time of transfer paper, etc.), it is preferable to change the applied voltage to discharge the toner having the same charge polarity in the charger onto the photosensitive member.

As the applied voltage at which the toner mixed in the charger is likely to be discharged, the peak-to-peak voltage of the AC component voltage value applied during image formation may be reduced, or the peak-to-peak voltage may be made the same. To lower the AC effective value, and more preferably, only the DC voltage component is applied.

By switching the applied voltage to apply only a DC voltage having the same polarity as that at the time of image formation, the charging device and the photosensitive member surface charged potential at which charging of the photosensitive member is slightly deteriorated due to mixing of transfer residual toner. The relationship between the potential difference of the toner and the triboelectric charge of the toner mixed into the charger and having the same polarity makes it possible for the mixed toner to be discharged onto the photoconductor and returned, and the residual toner remaining in the charger to be transferred. It is possible to prevent accumulation of mixed toner. Further, if the polarity of the potential generated on the photoconductor by the rubbing of the charging member and the photoconductor is opposite to the polarity of the potential placed on the photoconductor during image formation, a potential difference can be provided accordingly. This has the effect of discharging the mixed toner to the photoreceptor.

That is, at the time of image formation, an AC voltage is applied, the transfer residual toner is once taken into the charger, and the magnetic brush and the transfer residual toner are sufficiently rubbed, so that the charge polarity of the transfer residual toner is changed during the developing process. The polarity of the charge held by the toner is aligned, the AC voltage is stopped during non-image formation, and the DC voltage applied to the charging member is set between the charging potential of the charging member and the photosensitive member, and the frictional charging between the charging member and the photosensitive member is performed. By providing a potential difference due to the offset potential, making the absolute value of the potential on the photoconductor higher than the absolute value of the applied voltage, and returning the transfer residual toner mixed in the charging member to the photoconductor by the potential difference, the charging device The toner can be charged well over a long period of time without accumulating the mixed toner therein, and the image forming can be performed in a favorable state.

The potential on the surface of the photosensitive member, which is generated by rubbing the charging member and the photosensitive member, and the offset potential Vs
The absolute value of (V) is preferably in the range of 1 to 50 V, more preferably 5 to 45 V, and still more preferably 10 to 40 V.

If the voltage is less than 1 V, the potential difference between the photosensitive member surface potential and the charging member at the time of discharging the transfer residual toner is small, and the discharging effect is difficult to appear.
When it exceeds, the potential is hardly applied on the photoconductor at the time of image formation,
This is not preferable because image defects due to poor charging are likely to occur.

In the triboelectric charging between the charging member and the toner to be used, the tribo value of the toner has an absolute value of 1 to 90.
The range of mC / kg is preferable, and more preferably 5 to 80.
mC / kg, more preferably in the range of 10 to 40 mC / kg.

At 90 mC / kg or more, the reflection force between the charging member and the toner becomes strong, so that the toner hardly separates from the charging member, and it becomes difficult to discharge even with the electric field force due to the potential difference between the charging member and the photosensitive member. Is not preferred because
In the following, it is difficult to receive the influence of the electric field due to the potential difference between the charging member and the photoconductor, the toner hardly moves in the direction of the photoconductor at the time of discharging, and it becomes difficult to discharge.

The method for measuring the tribo will be described later.

Further, in order to recover the toner discharged on the photosensitive member in the developing step, in the case of reversal development, the toner is applied to the developing portion based on the absolute value Q1 of the potential of the photosensitive member at the developing portion on the discharged toner. The smaller the absolute value Q2 of the applied DC voltage, the stronger the electric field pulled to the developing unit and the easier it is to collect. If Q1 <Q2, it is difficult to collect the toner in the developing unit, and the discharged toner is taken into the charging member again, and the deterioration of the member is promoted.

In order to satisfy the relationship of Q1> Q2,
It is sufficient to lower the potential on the photoreceptor, and therefore, during non-image formation, the entire surface is exposed in the latent image forming process section, and by lowering the potential on the photoreceptor, the potential is applied to the developing section even during non-image formation. Thus, the transfer residual toner can be favorably collected without changing the applied bias during the image formation.

The same can be said for a roller or belt using a fur brush as the contact charging member.

Although there is no particular limitation on the developing means, in the case of an image forming apparatus having no cleaning means, a structure in which the developer and the photosensitive member are in contact with each other is preferable. Methods and the like are mentioned as suitable development methods. When the developer and the transfer residual toner are in contact on the photoreceptor, the rubbing force is added to the electrostatic force,
This is because there is a tendency that the transfer residual toner can be effectively collected by the developing unit.

In the present invention, in order to charge by directly injecting charges into the photoreceptor, a photoreceptor having a charge injection layer must be used.

In particular, when a magnetic brush using magnetic particles is used as a charging member and only a DC voltage is applied during non-image formation, the potential on the photosensitive member due to discharge is not charged up to the applied voltage, and the charging member and the photosensitive member are exposed accordingly. The potential difference between the toner and the body increases, and the transfer residual toner mixed into the charger is discharged, but the magnetic particles as the charging member tend to leak onto the photoreceptor. Therefore, it is better to use the injection charging method. preferable.

Therefore, from the above description, when the photosensitive member that performs charging by using discharge is used, the voltage applied to the charging member when discharging the toner mixed in the charger onto the photosensitive member is as follows. It is preferable that the absolute value of the voltage value is the same as the polarity applied at the time of image formation, and the absolute value of the voltage value is smaller than the absolute value of the frictional charging potential due to the rubbing of the charging member and the photoconductor.

When it is desired to perform good charge injection charging with the conventional photosensitive drum, the charge must be efficiently injected into a small number of trap points, so that the resistance value of the charging member is 1 ×.
It should be 10 ³ Ω or less, and the resistance value of the normal photosensitive drum surface material exceeds 1 × 10 ¹⁵ Ωcm,
In the case where the charge injection layer is provided, the area where electric charges can be retained on the surface of the photoreceptor increases, so that good charging can be performed even when a charging member having a higher resistance value is used. Actually, if the resistance value of the charge injection layer is in the range of 1 × 10 ⁸ to 1 × 10 ¹⁵ Ωcm, the photosensitive member surface potential charged with respect to the applied voltage is 90 even with a charging member of 1 × 10 ⁷ Ω. % Or more with good efficiency.

Accordingly, the photoreceptor according to the present invention includes:
It is important that the electrophotographic photosensitive member has a charge injection layer on the surface from which good charge injection chargeability can be obtained. At the same time, the volume resistivity of the charge injection layer on the surface of the photoreceptor is 1 × in order to satisfy the conditions for sufficient chargeability and image deletion.
It is necessary to use a photoreceptor having a range of 10 ⁸ to 1 × 10 ¹⁵ Ωcm. Preferably, the volume resistance value is 1 × 10 ¹¹ Ωcm to 1 × 10 ¹⁴ Ωcm from the viewpoint of image deletion and the like.
It is desirable to use one having a value of 0 ¹² Ωcm to 1 × 10 ¹⁴ Ωcm. If the density is less than 1 × 10 ¹⁰ Ωcm, image charge may not be held in the surface direction in a high humidity environment, causing image deletion.
^If it exceeds ¹⁵ Ωcm, the charge from the charging member cannot be sufficiently injected and retained, and the charging tends to be poor. By providing such a functional layer on the surface of the photoreceptor, it plays a role of retaining the charged electric charge injected from the charging member, and also plays a role of releasing this electric charge to the photoreceptor base during light exposure, thereby reducing the residual potential. .

As described above, in the present invention, while using a charging member having a medium resistance in order to prevent pinhole leakage and adhesion of the charging member to the photosensitive member, means for improving the charge injection charging efficiency to the photosensitive member are as follows. A charge injection layer for assisting charge injection to the photoconductor is provided on the surface of the photoconductor.

The charge injection layer is made of a material having a medium resistance by dispersing an appropriate amount of light-transmissive and conductive particles in an insulating binder, and an ionic conductive material having a high light-transmitting property in an insulating binder. mixing a resin having sex or constitute by copolymerizing, or the like which constitutes a resin alone with a photoconductive are contemplated medium resistance, any charge injection layer composed of these 10 ⁸ -10 ¹⁵ Ωcm
It is characterized by having a degree of resistance.

By adopting the above-described configuration, the charging by the charge injection, which would not otherwise occur unless the charging member had a resistance of 1 × 10 ³ Ωcm or less, and 1 × 10 ⁴
The prevention of pinhole leak, which could not be prevented unless it is not less than Ωcm, can be achieved.

Also, the present invention provides a good chargeability by charge injection which has not been produced unless a low-resistance charging member is used, and a pinhole on a photoreceptor which cannot be prevented by a low-resistance charging member. In order to simultaneously satisfy the characteristic of leakage due to the above, and to obtain sufficient potential convergence, the resistance value of the charging member that is charged by injection by contacting the photosensitive member having the charge injection layer is applied to the charging member. Voltage to V
(V), a potential VD (V) on the photoconductor when it enters a nip portion between the photoconductor and the charging member (upstream in the photoconductor moving direction viewed from the nip portion), and a voltage application portion of the charging member. When the electrophotographic charging device is such that the distance between the photosensitive member and the photosensitive member is d (cm), the dynamic resistance measurement method of the charging member in the dynamic resistance measuring method in which the charging member is brought into contact with the substrate of the rotating body of the conductor. V
The larger of the absolute value of −VD) / d and the absolute value of V / d is defined as electric field E (V / cm), and 20 to E (V / c).
m) within the applied electric field range of 10 ¹⁴
It is preferable to use a charging member in the range of Ωcm to ^{10 10} Ωcm.

FIG. 3 is a schematic diagram of an apparatus for measuring the dynamic resistance of the volume resistance of magnetic particles.

That is, the magnetic particles 37 are placed in the magnet enclosing sleeve 31 which is a magnetic particle holding member having a gap 34 of 0.5 mm from the aluminum drum 32 which is a conductive base so that the nip 33 between the magnetic drum 37 and the aluminum drum becomes 5 mm. Rotation of the charging member and the photoreceptor at the rotation speed and rotation direction at the time of actually forming an image by mounting, applying a DC voltage to the charging member, measuring the current flowing through the system to determine the resistance, Further, the volume resistance is calculated from the width of the gap 34, the nip 33, and the width of contact between the magnetic particles and the aluminum drum. In the figure, 35 is an ammeter and 36 is a power supply.

The resistance value of the charging member generally fluctuates depending on the applied electric field applied to the charging member. In particular, a high applied electric field has a low resistance, and a low applied electric field has a high resistance. Dependency is observed.

In the case where charging is performed by injecting electric charge into the photosensitive member, the surface to be charged with the photosensitive member enters the nip portion between the photosensitive member and the charging member (upstream from the charging member). In this case, the voltage difference between the charging potential of the photoconductor before entering and the voltage applied to the charging member is large, and therefore, the applied electric field applied to the charging member increases. However, when the photoreceptor passes through the nip portion, charges are injected into the photoreceptor, and charging is gradually performed in the nip portion, so that the potential on the photoreceptor gradually decreases to an applied voltage applied to the charging member. As the distance approaches, the difference between the applied voltage applied to the voltage application portion and the potential on the photosensitive member is small, and the difference approaches the direction of 0 V, so that the applied electric field applied to the charging member is correspondingly reduced. That is, in the step of charging the photosensitive member, the applied electric field applied to the charging member is different between the upstream side and the downstream side of the nip portion of the charging member, and the applied electric field applied to the charging member is high on the upstream side and low on the downstream side. .

Therefore, if a charge removal step such as pre-exposure is performed before the charging step, the potential on the photosensitive member when it enters the nip portion of the charging member is almost 0 V.
The applied electric field on the upstream side is almost determined by the applied voltage applied to the charging member. However, when a process for removing such charges is not provided, the applied voltage and polarity of charging and transfer, that is, the photosensitive after transfer, It is determined by the potential on the body and the applied voltage applied to the charging member.

That is, when charging is performed by injecting charges onto the photosensitive member, even if the resistance of the charging member is in the range of 10 ⁴ Ωcm to ^{10 10} Ωcm at a certain applied electric field, for example, 30 of the applied voltage applied to the charging member
% Applied electric field 0.3 × V /
If the resistance exceeds 10 ¹⁰ Ωcm in the range of d (V / cm) or less, charging due to injection at the downstream side of the nip portion of the charging member is significantly reduced. 70 of applied voltage
%, But the remaining 30% have poor charge injection properties, making it difficult to inject charges onto the photoreceptor, making it impossible to charge to a desired potential, resulting in poor charging. In other words, the resistance value when a lower electric field is applied has a great effect on the charge injection property to the photoconductor.

Therefore, the volume resistance of the charging member measured by the dynamic resistance measurement method is 10 ⁴ Ωcm to ¹⁰ 10 Ωcm.
Ωcm is preferable because a potential substantially equal to the applied voltage can be obtained on the photoconductor.

However, in the simultaneous cleaning (cleanerless) image forming method of the present invention, the potential on the photosensitive member and the potential (applied potential) of the contact charging member are at least somewhat higher (according to the knowledge of the present inventors, approximately 50 V or higher). When the potential difference of (1) occurs, the transfer residual toner controlled to the normal charging polarity in the charging member gradually leaks from the charging member during image formation, so that the negative memory due to the light blocking of the image exposure does not occur. It is necessary to stop the potential difference.

On the other hand, if the applied electric field at an applied voltage applied to the charging member becomes 10 ⁴ Ωcm or less, an excessive leakage current flows from the contact charging member to a flaw or a pinhole generated on the surface of the photoreceptor. As a result, poor charging in the surroundings, enlargement of pinholes, and destruction of current flow in the charging member occur.
Since the conductive layer (metal substrate) of the photoconductor is exposed on the surface of the scratches and pinholes on the photoconductor, the potential on the photoconductor is 0 V. Therefore, the maximum applied electric field applied to the charging member is It is determined by the applied voltage applied.

That is, even if the resistance value of the charging member is controlled within the range of 10 ⁴ Ωcm to ^{10 10} Ωcm at a certain applied electric field, poor charging and poor pressure resistance will result.

Therefore, in order to charge the photosensitive member, the maximum electric field applied to the charging member, that is, the voltage applied between the photosensitive member potential upstream of the charging member nip and the voltage applied to the charging member is determined. The applied electric field E (V / c), which is the larger of the electric field or the applied electric field determined by the applied voltage applied to the charging member when a pinhole is present due to a pre-exposure step or a scratch on the photoreceptor, etc.
m), the resistance value must be in the range of 10 ⁴ Ωcm to ^{10 10} Ωcm in the applied electric field range of 20 to E (V / cm).

Further, as the nip width between the charging member and the photosensitive member increases, the contact area between the charging member and the photosensitive member increases, and the contact time also increases. The charging is performed well. However, in order to obtain a sufficient charge injecting property even when the nip width is narrowed, the resistance of the charging member is set to R1 and R2 of the resistance due to the applied electric field within the range of the applied electric field.
/ R2 ≦ 1000 is preferable. In the process performed in the charging nip, because the resistance changes rapidly, the injection of the charge to the photoconductor does not follow, passes through the nip portion, and may not be sufficiently charged. is there.

In the present invention, as described above, the triboelectric charging polarity of the contact charging member with the photoreceptor is opposite to the charging polarity of the photoreceptor, and the triboelectric charging polarity with the toner of the charging member is set at the time of image formation. It is preferably the same as the polarity of the potential on the body.

According to the knowledge of the present inventors, the charging potential of the photosensitive member in the charging step by charge injection is obtained by adding the triboelectric charging of the contact charging member with the photosensitive member to the injecting property. Appears remarkably when the photoreceptor is charged by applying only. If the polarity of the frictional charging of the contact charging member with the photoreceptor is opposite to the charging polarity of the photoreceptor, applying only a DC voltage of the same polarity during image formation during non-image formation lowers the photoreceptor potential by the amount of frictional charge. Then, the charging member and the toner are sufficiently rubbed in the charging member by the electric field difference, and the mixed toner in which the charge of the transfer residual toner is sufficiently the same polarity as the charge in the developing process is discharged onto the photosensitive member. Is done well,
It is possible to prevent accumulation of the transfer residual toner in the charger, and accordingly, good charging is performed over a long period.

Further, by bringing the charging member into sufficient contact with the photoreceptor, the charging property is improved, and the chance of discharging the toner mixed in the charging device onto the photoreceptor is increased.
It is preferable that the charging member is moved with respect to the photosensitive member with a difference in speed.

The average particle size of the magnetic particles used for the charging member is preferably 5 to 200 μm. If it is smaller than 5 μm, the magnetic brush is likely to adhere to the photoreceptor.
If it is larger than m, the density of spikes of the magnetic brush on the sleeve cannot be increased, and the chargeability for injection into the photoreceptor tends to deteriorate. More preferably, it is 10 to 100 μm, and more preferably, 10 to 50 μm.

The average particle size of the whole was determined by using a laser diffraction type particle size distribution measuring device HEROS (manufactured by JEOL Ltd.).
The range of 0.05 μm to 200 μm was measured by dividing 32 logarithms, and the 50% average particle size was defined as the average particle size.

The gap between the holding member for holding the magnetic particles and the photosensitive member is preferably in the range of 0.2 to 2 mm. 0.2
If the diameter is smaller than 1 mm, the magnetic particles do not easily pass through the gap, and the magnetic particles are not smoothly transported on the holding member, and poor charging or excessive accumulation of the magnetic particles in the nip portion, which is likely to adhere to the photoconductor. If it exceeds 2 mm, it is not preferable because it is difficult to form a wide nip width between the photoconductor and the magnetic particles. More preferably, 0.2 to 1 mm, further preferably 0.3
~ 0.7 mm is preferred.

The magnetic particles according to the present invention are made of a magnetic material such as iron, cobalt, nickel, etc., which are made to stand by magnetism and are charged by bringing the magnetic brush into contact with the photosensitive member. An alloy or compound containing an element, a ferrite whose composition is adjusted by performing an oxidation treatment, a reduction treatment, or the like, for example, a composition adjusted, a hydrogen-reduced Zn—Cu ferrite, or the like is used. In order to keep the resistance of ferrite within the above-mentioned range within the range of the applied electric field or less as described above, it is achieved by adjusting the composition of the metal. Generally, when a metal other than divalent iron increases, the resistance becomes The resistance tends to drop sharply.

The magnetic particles used in the present invention preferably have a surface layer in order to exhibit the above triboelectric charging polarity. The form of the surface layer is such that the surface of the magnetic particles is coated with a vapor-deposited film, a conductive resin film, a conductive pigment-dispersed resin film, or the like. The surface layer does not necessarily need to completely cover the magnetic particles, and the magnetic particles may be exposed as long as the effects of the present invention can be obtained. That is, the surface layer may be formed discontinuously.

Further, from the viewpoint that the triboelectric charge polarity can be easily controlled, a resin coating obtained by adding a conductive pigment to various resins for resistance adjustment is preferable, and from the viewpoints of productivity, cost and the like, the conductive pigment-dispersed resin is preferably used. It is preferred to coat the membrane.

Further, from the viewpoint of suppressing the electric field dependence of the resistance value, it is preferable to coat a high resistance binder resin with a resin film in which an electron conductive conductive pigment is dispersed.

As a matter of course, the resistance of the magnetic particles after coating must be within the above-mentioned range, and furthermore, the resistance drops sharply on the high electric field side, and depends on the size and depth of the scratch on the photoreceptor. From the viewpoint of widening the allowable range of the leak image generation, it is preferable that the resistance of the base magnetic particles also falls within the above range.

Examples of the binder resin used for coating the magnetic particles include styrenes such as styrene and chlorostyrene; monoolefins such as ethylene, propylene, butylene and isobutylene; vinyl acetate, vinyl propionate, vinyl benzoate and acetic acid. Vinyl esters such as vinyl; α-methylene such as methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate Aliphatic monocarboxylic acid ester vinyl methyl ether,
Vinyl ethers such as vinyl ethyl ether and vinyl butyl ether; homopolymers and copolymers of vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, and vinyl isopropenyl ketone; and particularly typical binder resins include conductive resins. Polystyrene, styrene-alkyl acrylate copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-anhydrous maleic, etc., from the viewpoints of dispersibility of conductive fine particles, film forming property as a coating layer, and productivity. Acid copolymers, polyethylene, and polypropylene are exemplified. Further, polycarbonate, phenol resin, polyester, polyurethane, epoxy resin, polyolefin, fluorine resin, silicone resin, polyamide and the like can be mentioned.

For example, examples of the fluororesin include polyvinyl fluoride, polyvinylidene fluoride, polytrifluoroethylene, polychlorotrifluoroethylene, polydichlorodifluoroethylene, polytetrafluoroethylene, polyhexafluoropropylene, and other monomers. And a solvent-soluble copolymer in which is copolymerized.

Examples of the silicone resin include KR271, KR282 and KR31 manufactured by Shin-Etsu Silicone Co., Ltd.
1, KR255, KR155 (straight silicone varnish), KR211, KR212, KR216, KR2
13, KR217, KR9218 (silicone varnish for modification), SA-4, KR206, KR5206 (silicone alkyd varnish), ES1001, ES1001
N, ES1002T, ES1004 (silicone epoxy varnish), KR9706 (silicone acrylic varnish), KR5203, KR5221 (silicone polyester varnish) and SR2100 manufactured by Toray Silicone Co., Ltd.
SR2101, SR2107, SR2110, SR21
08, SR2109, SR2400, SR2410, S
R2411, SH805, SH806A, SH840 and the like are used.

In order to control the triboelectric charging polarity of the magnetic particles with respect to the toner and the photosensitive member, a binder resin may be appropriately selected from the above resins and the like.

Further, a resin film in which a conductive pigment is dispersed may be formed for resistance adjustment.

The conductive fine particles according to the present invention include:
Metals such as copper, nickel, iron, aluminum, gold, and silver; and metal oxides such as iron oxide, ferrite, zinc oxide, tin oxide, antimony oxide, and titanium oxide; and electron conductive powders such as carbon black. In addition, examples of the ion conductive agent include lithium perchlorate and quaternary ammonium salts.

As a matter of course, in the final form of the resin coating layer, the polarity of the magnetic particles charged on the toner and the photosensitive member must be controlled.

In order to easily control the electrode properties and the triboelectric charge polarity, the surface of the magnetic particles may be coated with a coupling agent which is a compound having hydrophilicity and a hydrophobic group. In the case of the coupling agent, an extremely thin film (at the molecular level) is formed on the surface of the magnetic particles, so the influence on the resistance value of the magnetic particles is small. The process of resistance adjustment may not be performed.

Examples of the coupling agent include titanate, aluminum and silane coupling agents.
Various functional groups such as an amino group may be introduced in order to control the tribo of the toner or the triboelectric charging polarity to the photoconductor.

As described above, the photoreceptor according to the present invention has a volume resistance of 1 × in the layer farthest from the support in order to satisfy the conditions for sufficient chargeability and image deletion as described above. A photoreceptor provided with a charge injection layer in the range of 10 ⁸ Ωcm to 1 × 10 ¹⁵ Ωcm must be used. Desirably, the volume resistance value is 1 × 10 ¹¹ Ω from the viewpoint of image deletion and the like.
cm to 1 × 10 ¹⁴ [Omega] cm, when also considering further environmental fluctuation of the volume resistivity, volume resistivity 1 × 10 ¹² Ωcm~1 ×
It is desirable to use one of 10 ¹⁴ Ωcm. 1 × 10 ¹⁰
If it is less than Ωcm, the charged charge is not retained in the surface direction in a high humidity environment, causing image deletion. If it exceeds 1 × 10 ¹⁵ Ωcm, the charged charge from the charging member cannot be sufficiently injected and retained, and the charging tends to be poor. . By providing such a functional layer on the surface of the photoreceptor, it plays a role of retaining the charged electric charge injected from the charging member, and also plays a role of releasing this electric charge to the photoreceptor base during light exposure, thereby reducing the residual potential. . Further, by employing such a configuration by using the charging member and the photoconductor according to the present invention, the charging start voltage Vh is small, and the charging potential of the photoconductor is charged to almost 90% or more of the voltage applied to the charging member. It is now possible to do that. For example, the charging member of the present invention has an absolute value of 100
When a DC voltage of ２０００2000 V is applied, the charging potential of the electrophotographic photoreceptor having the charge injection layer of the present invention is raised to an applied voltage of 8
It can be 0% or more, further 90% or more. On the other hand, the charging potential of the photoconductor obtained by charging using conventional discharge is almost 0 V when the applied voltage is 640 V or less, and is 640 V or more when the applied voltage is 640 V or more.
Only about the charging potential of the value obtained by subtracting V was obtained.

Here, the method of measuring the volume resistance value of the charge injection layer is as follows. A charge injection layer is formed on a polyethylene terephthalate (PET) film having a conductive film deposited on the surface thereof, and this is used as a volume resistance measurement device (Hewlett Packard Co., Ltd.). Made 41
The measurement is performed by applying a voltage of 100 V in an environment of 23 ° C. and 65% at 40 B pAMATER).

The charge injection layer is composed of an inorganic layer such as a metal vapor-deposited film or a conductive powder resin dispersion layer in which conductive fine particles are dispersed in a binder resin.
The conductive powder resin dispersion film is formed by applying a suitable coating method such as a dipping coating method, a spray coating method, a roll coating method, and a beam coating method. In addition, a resin formed by mixing or copolymerizing a resin having high light transmittance and ionic conductivity with an insulating binder, or a resin having a medium resistance and photoconductive resin alone may be used. In the case of the conductive fine particle dispersed film, the addition amount of the conductive fine particles is 2 to 250 parts by mass with respect to 100 parts by mass of the binder resin.
More preferably, the amount is 2 to 190 parts by weight. When the amount is less than 2 parts by mass, it is difficult to obtain a desired volume resistance value. When the amount is more than 250 parts by mass, the film strength is reduced and the charge injection layer is easily scraped off, and the life of the photoconductor is shortened. This is because the resistance tends to be short, and the resistance is low, so that an image defect is likely to occur due to the flow of the latent image potential.

The binder of the charge injection layer can be the same as the binder of the lower layer, but in this case, the coating surface of the charge transport layer may be disturbed at the time of coating the charge injection layer. Therefore, it is necessary to particularly select a coating method.

In the present invention, the charge injection layer preferably contains lubricant particles. The reason for this is that the friction between the photoreceptor and the injected charging member is reduced during charging, which increases the charging nip and improves charging characteristics, and minimizes the transfer of transfer residual toner to the charging member due to the cleaner-less system. This is also for the purpose of improving the transfer efficiency from the viewpoint of reducing the amount. In particular, it is more preferable to use a fluororesin, a silicone resin, or a polyolefin resin having a low critical surface tension as the lubricant particles. More preferably, a tetrafluoroethylene resin (PTFE) is used. In this case, the addition amount of the lubricant particles is preferably 2 to 50 parts by mass, and more preferably 5 to 40 parts by mass with respect to 100 parts by mass of the binder. When the amount is less than 2 parts by mass, the amount of the lubricant powder is not sufficient, so that the charging characteristics are not sufficiently improved. When the amount is more than 50 parts by mass, the resolution of the image and the sensitivity of the photoreceptor are greatly reduced. .

In the present invention, the thickness of the charge injection layer is 0.1
The thickness is preferably from 10 to 10 μm, particularly preferably from 1 to 7 μm.

Hereinafter, the toner triboelectric charge and the offset potential of the photoreceptor for the members used in the present invention will be described.

The developer is a two-component developing method using a Cu-Zn ferrite carrier whose surface has an average particle diameter of 50 μm coated with a silicone resin and a developer comprising a non-magnetic toner positively charged to the carrier. And The toner and the carrier were mixed at a weight ratio of 5: 100.

Three types (Ta, Tb, Tc) of non-magnetic toners having the above-mentioned positive chargeability were prepared.

As for the magnetic particles as the charging member, a Cu—Zn ferrite carrier (Fe ₂ O ₃ / CuO) having an average particle size of 25 μm was used as a core carrier before resin coating.
/ Mole ratio of each metal oxide of ZnO is 2.1:
1: 1), and a resin-coated carrier 3 whose resistance is adjusted by dispersion of conductive pigment with three different resins.
Types (Ca, Cb, Cc) were prepared. FIG. 4 shows the resistance value of each dynamic resistor. The resistance was measured under an environment of 23 ° C. and a relative humidity of 60%.

A fur brush (Ba) made of a conductive resin fiber having a fiber diameter of 10 μm and a flock density of 250,000 fibers / inch ² with adjusted resistance was prepared as a fur brush as a charging member. FIG. 4 shows the resistance value of the dynamic resistance of the fur brush. The resistance was measured under an environment of 23 ° C. and a relative humidity of 60%.

As the photosensitive member, two types of negatively chargeable photosensitive members having a charge injection layer adjusted by dispersing conductive fine particles to a resistance value of 5 × 10 ¹² Ωcm with different binder resins (Da, Db) ) Was prepared.

Table 1 below summarizes the toner triboelectric charge amount of the magnetic particles as the charging member and the polarity of the offset potential of the photosensitive member according to each combination.

The triboelectric charge polarity of the fur brush with respect to the toner was measured by molding the conductive resin used for the fur brush into pellets and finely pulverizing the same into a powder having a particle size of about 30 μm.

The measuring method is as follows.

(Measurement Method 1) FIG. 2 is a schematic diagram of a measurement apparatus for measuring a triboelectric charge amount of a magnetic particle serving as a charging member with respect to a toner. The measuring method is as follows. Under an environment of 23 ° C. and a relative humidity of 60%, 0.04 kg of the magnetic particles to be measured is added to 0.04 kg of the toner.
The mixture 20 to which 28 kg has been added is placed in a polyethylene bottle having a volume of 50 to 100 ml, left overnight in the above environment, and shaken by hand shaking 150 times. Next, 0.0005 kg of the mixture is put into a metal measuring container having a screen 23 of 500 mesh at the bottom, and a metal lid 24 is placed. At this time, the weight of the entire measurement container 22 was measured, and W1
kg. Next, using a suction machine (at least a portion in contact with the measurement container 22 is an insulator), suction is performed from the suction port 27,
Adjust the air volume control valve 26 to increase the pressure of the vacuum gauge 25 to 250 m.
mAq. In this state, suction is performed for 3 minutes to remove the developer. The potential of the electrometer 29 at this time is set to V (volt). Here, 28 is a capacitor, and the capacity is C (mF). Also, the weight of the entire measuring machine after suction is measured and is set to W2 kg. The tribo value of this developer (mC /
kg) is usually calculated as in the following formula.

Amount of triboelectric charge (mC / kg) = CV / (W1−W2)

However, since the magnetic particles used in the present invention have a small particle size, even a 500-mesh screen can pass through a considerable amount of the mesh. Therefore, it is considered that the magnetic particles passing through the mesh are canceled by the triboelectric charge of the toner. , Including the correction. The mass of the magnetic particles weighed in advance is M1, and the mass of the toner is M1.
2, and M3 of this mixture was used as a metal measuring container 2.
2 When triboelectric charge (mC / kg) = CV / (M3 × M2 / (M
1 + M2)).

The triboelectric charge of the toner was measured as described above.

(Measurement Method 2) The method of measuring the triboelectric charge (offset potential of the photoconductor) of the magnetic particles serving as the charging member with respect to the photoconductor is as follows. Then, the charging member and the photoreceptor were rotated under the same conditions as the endurance conditions with only the magnetic particles attached (removal of the transfer portion and the development portion), and an electrometer was arranged at the development position, and the offset potential of the photoreceptor was measured.

[0099]

[Table 1]

[0100]

【Example】

(Examples 1 to 5) Examples of the present invention will be specifically described below, but the present invention is not limited thereto.

FIG. 1 shows a schematic view of the electrophotographic apparatus of the present invention.

Digital copier using a laser beam as the electrophotographic apparatus of the present invention (GP55, manufactured by Canon Inc.)
Was prepared. An outline of the apparatus is provided with a corona charger as a charging means for a photoreceptor, a one-component developing device employing a one-component jumping developing method as a developing means, a corona charger as a transfer means, a blade cleaning means, and a pre-charge exposure. Means. The photosensitive member, the charger, the cleaning means, and the photosensitive member are an integrated unit (process cartridge). Process speed is 150m
m / s. The apparatus was modified as follows to obtain an image forming apparatus of a cleanerless system.

The developing portion was modified from a one-component jumping development to a two-component developer.
A conductive non-magnetic sleeve of φ16 including a magnet roller is disposed on the charged portion to form a charging magnetic brush. Furthermore, the transfer means using the corona charger was changed to a roller transfer method, the pre-exposure means and the cleaning blade were removed, and an electronic device of a reversal developing cleanerless system using a negatively charged photoreceptor and a negatively charged toner was used. It was a photographic device.

In FIG. 1, 10 is a developer, 11 is a magnetic brush charger, 12 is a photoreceptor, 13 is exposure light, 14 is a transfer roller, 15 is a magnetic brush, 16 is a conductive non-magnetic sleeve containing a magnet, 17 Denotes a developing sleeve, 18 denotes a developing device, and 19 denotes a stirring screw.

The gap between the conductive sleeve of the charged portion and the photosensitive member was set to 0.5 mm. The developing bias is -5.
DC component of 00 V (-for both image formation and non-image formation
A rectangular wave of 1000 Vpp / 3 kHz is superimposed on (500 V applied).

(Evaluation Method) Using the above electrophotographic apparatus,
A4 solid black image continuous 5 at 23 ° C and 60% relative humidity
Performed image durability of 00 sheets, collected the magnetic particles after the durability from the conductive non-magnetic sleeve, and from the analysis with a thermobalance,
The amount of toner mixed into the charging member was measured. Specifically, the amount of contamination was measured from the decrease in weight from 150 ° C. to 800 ° C. in a nitrogen atmosphere. The weight loss amount of each of the magnetic particles and the toner before the endurance used in the endurance was C1.
(Wt%) and T1 (wt%), and the amount of reduction of the charging member after durability was C2 (wt%), the amount of contamination was measured by the following formula.

The amount of mixing X (wt%) = 100 (C2−C1) / T1

The endurance conditions are as follows. Magnetic particles as charging members are mounted on a conductive non-magnetic sleeve so that a charging nip having a width of about 3 mm is formed between the magnetic particles and the photosensitive member.
The charging device is driven at 150 mm / s at a peripheral speed of 450 mm / s.
The photoreceptor was rotated at a peripheral speed of s, and the voltage of the charging member was applied (the DC voltage component was fixed at -700 V for both image formation and non-image formation) to achieve durability. During non-image formation, the exposure in the latent image forming step was turned off.

The combinations of the magnetic particles, toner, and photoreceptor used as the charging member used for image endurance were set as combinations 1, 2, 4, 5, and 8 in Table 1, and the voltage applied to the charging member was changed to the image. 0.7 kV as an AC component during formation
pp (peak-to-peak voltage) is superimposed, and the AC line segment is turned off during non-image formation (e.g., between paper sheets, front and rear rotations) to -700.
Durability was performed by applying only a DC voltage of V, and the amount of mixed toner after the durability was checked. Table 2 summarizes the results.

(Comparative Examples 1-4) Combinations of magnetic particles, toner, and photoreceptor, which are charging members used for image-forming durability, are shown as combinations 3, 5, 6, and 9 in Table 1, respectively.
The voltage applied to the charging member is superimposed with 0.7 kVpp as an AC component at the time of image formation, and the AC line segment is turned off at the time of non-image formation (for example, at the time of inter-sheet, front, and post-rotation) to perform durability. Thereafter, the amount of mixed toner was checked. Table 2 summarizes the results.

(Examples 6 and 7) Combinations of magnetic particles, toner, and photoreceptor, which are charging members used for image output durability, are shown as combinations 2 and 5 in Table 1, respectively. During image formation and non-image formation, durability was performed by superimposing 0.7 kVpp as an AC component, and the amount of mixed toner after the durability was checked. Table 2 summarizes the results.

(Embodiment 8) The combinations of the magnetic particles, toner, and photoreceptor used as the charging member used for image output durability were set as combination 5 in Table 1, and the voltage applied to the charging member was changed to AC during image formation. 0.7 kVpp is superimposed as a component, and at the time of non-image formation (for example, at the time of inter-sheet, front, and post-rotation), the AC line segment is turned off and durability is performed by applying only a DC voltage of -300 V. Checked the amount. Table 2 summarizes the results.

Example 9 The combinations of the magnetic particles, toner, and photoreceptor used as the charging member used for image formation durability were set as combination 5 in Table 1, and the voltage applied to the charging member was set to a value that was not applied during image formation. At the time of image formation (for example, at the time of paper interval, at the time of front rotation, and at the time of post rotation), durability was performed by applying only a DC voltage of -700 V, and the amount of mixed toner after the durability was checked. Table 2 summarizes the results.

Example 10 Combinations of a charging member, a toner, and a photoreceptor used for image output durability were each set to combination 10 in Table 1, and the voltage applied to the charging member was set to 0.1 as an AC component during image formation. 7 kVpp was superimposed, the AC component was turned off during non-image formation (e.g., between sheets, before and after rotation), and durability was performed by applying only a -700 V DC voltage, and the amount of mixed toner after the durability was checked. Table 2 summarizes the results.

In addition, the evaluation machine uses a φ16 conductive non-magnetic sleeve having a magnet roller in the charging portion, and a nip with a photosensitive member having a width of 1 cm from a charging brush using a fur brush to a charging member using a fur brush. Adjust
In the evaluation method, the weight of the entire fur brush before and after the endurance was measured, and the amount of the mixed toner was calculated from the following equation, with the weight before the endurance being B1 and the weight after the endurance being B2.

Amount X (wt%) = 100 × (B2−B1) / B1

Comparative Example 5 The same evaluation as in Example 10 was performed except that the combination of the charging member, the toner, and the photoreceptor used for image output durability was changed to combination 11 in Table 1. Table 2 summarizes the results.

[0118]

[Table 2]

[0119]

As described above, according to the present invention, even when image formation is performed by a cleaner-less system, a good image can be obtained because the transfer residual toner is well collected in the development step. In addition, since the transfer residual toner is less mixed into the charging member, deterioration of the charging member is suppressed, and therefore, an image forming method capable of obtaining an excellent charging property and an image over a long period of time can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a schematic configuration of an image forming apparatus that performs an image forming method of the present invention.

FIG. 2 is a diagram illustrating a schematic configuration of an apparatus for measuring a triboelectric charge amount of toner.

FIG. 3 is a diagram showing a configuration of a dynamic resistance measuring device for measuring a volume resistance value of a charging member according to the present invention.

FIG. 4 is a diagram illustrating a relationship between a volume resistance value of a charging member and an applied electric field.

Continuation of the front page (72) Inventor Yoshifumi Hano 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (19)

[Claims] 1. A charging step of charging a photosensitive member by applying a voltage to a charging member arranged in contact with the electrophotographic photosensitive member, and an electrostatic latent image on the photosensitive member by exposing the charged photosensitive member. A latent image forming step of forming a toner image, a developing step of reversal developing the obtained electrostatic latent image with toner, and a transfer step of transferring the obtained toner image to a transfer material. In the image forming method for recovering the remaining toner by a developing process, the polarity of a potential generated on the photoconductor by rubbing the charging member and the photoconductor is a polarity of a potential for charging the photoconductor during image formation. And the polarity of the charge generated in the toner when the toner is rubbed with the charging member is the same as the polarity of the potential for charging the photoreceptor during image formation. Image shape Method. 2. The image forming apparatus according to claim 1, wherein the transfer member retains the transfer residual toner during image formation, moves the toner from the charge member onto the photosensitive member during non-image formation, collects the toner in a developing device, and reuses the toner. The image forming method as described in the above. 3. The image forming apparatus according to claim 2, wherein the voltage applied to the charging member is changed between the time of image formation and the time of non-image formation in order to move the toner from the charging member onto the photosensitive member during non-image formation. Image forming method. 4. The image forming method according to claim 3, wherein the voltage applied to the charging member is a voltage obtained by superimposing an AC voltage on a DC voltage during image formation, and only a DC voltage is applied during non-image formation. 5. The relationship between the absolute value Q1 of the potential on the photoreceptor in the developing step during non-image formation and the absolute value Q2 of the DC voltage applied to the developing step during non-image forming is Q1> Q2. The image forming method according to any one of claims 1 to 4, wherein the applied voltage is as follows. 6. The electrophotographic photoreceptor according to claim 1, further comprising a charge injection layer having a volume resistivity of 1 × 10 ⁸ to 10 ¹⁵ Ωcm farthest from the support of the photoreceptor. Image forming method. 7. The image forming method according to claim 6, wherein the charge injection layer contains a light transmitting and insulating binder and conductive particles. 8. The conductive particles contained in the charge injection layer are S
The image forming method according to claim 7, wherein nO ₂ is a main component. 9. The image forming method according to claim 6, wherein the charge injection layer contains a lubricating powder. 10. The image forming method according to claim 9, wherein the lubricating powder is a fluororesin, a silicone resin or a polyolefin resin. 11. The voltage applied to the charging member is V, the potential on the photoconductor when it enters the nip portion between the photoconductor and the charging member is VD, and the voltage application portion of the contact charging member and the photoconductor are Is the distance d, the volume resistance of the charging member according to the dynamic resistance measurement method is the absolute value of (V−VD) / d and V
E (V / c)
The image forming method according to any one of claims 1 to ¹⁰ , wherein the applied electric field is 10 ⁴ Ωcm to ^{10 10} Ωcm in the applied electric field range of 20 to E (V / cm) when m). 12. The image forming method according to claim 11, wherein the charging member has a resistance characteristic such that a ratio R1 / R2 of the maximum value R1 and the minimum value R2 of the volume resistance value of the charging member is 1000 or less. 13. The image forming method according to claim 1, wherein the charging member moves at a peripheral speed difference with respect to the electrophotographic photosensitive member. 14. The charging member is made of magnetic particles, and the magnetic particles have an average particle size of 5 to 200 μm.
3. The image forming method according to any one of 3. 15. The image forming method according to claim 14, wherein the magnetic particles have a surface layer on the core particles. 16. The image forming method according to claim 15, wherein the surface layer of the magnetic particles contains a conductive resin or a conductive particle and a binder resin. 17. The image forming method according to claim 1, wherein the charging member is a roller or a belt using a fur brush. 18. The image forming method according to claim 17, wherein the fur brush contains a conductive resin, or conductive particles and a binder resin. 19. The image forming method according to claim 1, wherein the transfer step is performed by a contact transfer unit.