JPH11352755A - Method for regenerating magnetic particles for electrification, regenerated magnetic particles for electrification and device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make used magnetic particles for electrification regenerable by washing out and removing a sticking matter with a solvent after using the magnetic particles for electrification used in a device for electrifying an electrophotographic photoreceptor to specified potential. SOLUTION: Magnetic substance whose electrifying characteristic for the photoreceptor is lowered by a sticking matter because of its use for electrifying the photoreceptor, is recovered and the sticking matter is washed out and removed with the solvent. A good result is obtained in the case of using an aromatic compound or ketones and the like out of various solvents, and a very excellent result is obtained by using toluene, especially, out of them. Furthermore, it is desirable to apply physical force such as ultrasonic vibration (>=10 kHz oscillating frequency is desirable), stirring or flow at the time of washing out with the solvent, and the much better effect is obtained by excessively heating the solvent or utilizing the vapor of the solvent. Furthermore, it is desirable to process the surface of the magnetic particle with a coupling agent having an alkyl chain whose carbon number is six or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of reproducing magnetic particles for charging used in a charging device for charging an electrophotographic photosensitive member, and further relates to a magnetic particle for charging reproduced by the method and an apparatus using the same. About.

[0002]

2. Description of the Related Art Conventionally, many methods are known as electrophotography. In general, a photoconductive substance is used to form an electric latent image on a photoreceptor by various means. The latent image is developed into a visible image by developing with toner, and the toner image is transferred to a transfer material such as paper as necessary, and then the toner image is fixed on the transfer material by heat or pressure to obtain a copy. Things. Further, toner particles remaining on the photoconductor without being transferred onto the transfer material are removed from the photoconductor by a cleaning process.

As a means for charging a photosensitive member in such an electrophotographic method, a means utilizing so-called corona discharge is often used. On the other hand, elastic means such as a roller (charging roller) and a blade (charging blade) are used. Conductive member having a body, a conductive member (charged fur brush) formed by brushing fibers and the like subjected to a conductive treatment, and a conductive member (charged magnetic brush) holding magnetic particles in a brush shape by a magnet body ) Or the like as a charging means of a photoreceptor (for example, JP-A-59-133569, JP-A-6-30).
No. 1265 and JP-A-7-72667)
Many have been developed. According to these techniques, when a conductive member is brought into contact with the surface of a photoreceptor and a narrow space is formed in the vicinity of the contact portion, when a voltage is applied to the conductive member, a discharge that can be interpreted according to Paschen's law is generated. Ozone generation can be suppressed as much as possible, so that a means for capturing ozone is unnecessary or reduced, so that downsizing and cost reduction of the apparatus can be achieved.

Further, as another attempt, a voltage is applied by bringing a conductive member such as the charging roller, the charging fur brush and the charging magnetic brush into contact with the photoreceptor, and a charge is applied to a trap level on the surface of the photoreceptor. A technique for performing contact injection charging by injection is being studied.

[0005] In these so-called contact charging members, in order to uniformly charge the photosensitive member regardless of the form of the charging member or the device, the contact state between the charging member and the photosensitive member is required. It is necessary to keep the charging member as uniform as possible, and for that purpose, it is necessary to press the charging member against the photosensitive member with a constant pressure. In particular, in a charging member using an elastic body or a fiber, a relatively large pressure is required to ensure a uniform contact state, and therefore, a phenomenon in which the toner is pressed against the photoconductor and adheres (fusion). Tend to occur. On the other hand, in the case of the charged magnetic brush, since the contact portion with the photoreceptor is formed by countless small magnetic particles, so large pressure is not required to obtain a uniform contact state, so that fusion occurs. Is greatly reduced.

In addition, in the charging method by charge injection, since the discharge does not accompany, the influence of the photoreceptor shaving and the so-called discharge products can be reduced or ignored.
There is an advantage that the electrophotographic apparatus is advantageous for long-term use.

[0007] From such a viewpoint, particularly in recent years, for example, Japanese Patent Application Laid-Open Nos. 8-6355 and 8-6
Particularly, as disclosed in JP-A-9149, JP-A-8-69155, JP-A-8-69156 and JP-A-8-106200, a study of a magnetic brush contact injection charging device using magnetic particles has been conducted. Is being actively conducted.

The magnetic particles for charging used for charging the photoreceptor have a toner component or a photoreceptor on the surface of the magnetic particles due to heat generated by contact / rubbing between the particles or contact / rubbing with a developer. A film of the deposit consisting of the components is formed, and so-called spent occurs. Therefore, as the usage time of the magnetic particles for charging increases, the characteristics of charging the photoreceptor decrease, and the photoreceptor becomes unsuitable for practical use. It has been proposed to treat the surface of the magnetic material to reduce this phenomenon as much as possible, and although the effect of extending the use time is recognized, deterioration of the characteristics due to spent is still inevitable.

Conventionally, such a member with reduced characteristics is
Although collected and discarded, the importance of material design on the premise of reuse is increasing from the viewpoint of consideration for the environment and effective use of resources. It is widely known that magnetic particles used in electrophotography are mainly used as a developer for carrying a toner and developing an electrostatic latent image. JP-A-47-12286, JP-A-63-21294
No. 5, JP-A-6-149132 and JP-A-7-149132
Japanese Unexamined Patent Publication No. 3-26565 and JP-A-6-149132 disclose techniques relating to regeneration of a developer by heat treatment, and JP-A-3-89254 and JP-A-6-149132 disclose techniques relating to regeneration of a developer by solvent washing. JP-A-7-28
Japanese Patent Publication No. 280 proposes a technique relating to regeneration of a developer by mixing an abrasive.

However, in the heat treatment, for example, in order to suppress a change in the characteristics of the magnetic particles themselves, there are restrictions such as a narrow range of usable heating conditions, a need to repeat a plurality of times, and a complicated process. Yes, it may be problematic in terms of versatility and cost. On the other hand, in the solvent treatment, there is a problem in terms of practicability because the solvent that can be used is restricted due to the balance with the surface coating material. There is a problem that it is unsuitable for use. Furthermore, in the mixing of the abrasive, not only must the abrasive, the stirrer, the stirring conditions, etc. be taken into consideration in order to prevent damage to the magnetic particle surface (especially a coated product), but also the step of separating the abrasive after the treatment is required. This is necessary, and the possibility of cost increase due to complicated processes cannot be denied.

In addition, all of the methods are based on the premise that magnetic particles are regenerated as a developer. In these techniques, naturally, from the viewpoint of preferable characteristics, composition and effect as a developer. Although studies have been made, no study has been made on magnetic particles as a completely different application (that is, a photoreceptor charging application).

Incidentally, the cleaning step in the conventional electrophotographic process generally includes blade cleaning, fur brush cleaning and roller cleaning. In either method, the cleaning member is pressed against the photoreceptor to mechanically scrape off the transfer residual toner, or dampen and collect it in a waste toner container. Therefore, a problem caused by the pressing of the cleaning member against the surface of the photoconductor (for example, the pressing of the cleaning member strongly wears the photoconductor and shortens the life of the photoconductor) may occur. On the other hand, from the viewpoint of the apparatus, the provision of such a cleaning apparatus inevitably increases the size of the apparatus, making it difficult to reduce the size of the apparatus. In order to solve these problems and achieve effective use of toner from the viewpoint of miniaturization of the apparatus and ecology, it has been desired to develop a system that does not generate waste toner.

As a countermeasure to this, there is a technique called simultaneous development cleaning or cleanerless. In order to realize a cleaner-less system, for example, as disclosed in Japanese Patent Application Laid-Open No. 8-240925, the toner remaining after transfer is controlled to the same polarity as the photoconductor using a photoconductor charging corona and discharge, and the reversal development method is used. Performing simultaneous development and cleaning is one method.

However, if a magnetic brush is used as the charger, the corona or discharge at the time of charging the photoreceptor is not used.
While controlling the polarity of the toner remaining after transfer by frictional charging,
The photoconductor can be charged. Known techniques include:
For example, JP-A-4-21873 and JP-A-6-11
0253, JP-A-6-118855, JP-A-8-22150, JP-A-8-69155, JP-A-9-288407, JP-A-9-288
As disclosed in JP-A-408-408 and JP-A-9-288409, a number of cleanerless technologies using a magnetic brush charging device have been studied. According to these techniques, transfer residual toner on the photoconductor (affected by transfer,
The toner remaining after transfer is frictionally charged between the magnetic particles and the toner constituting the magnetic brush while charging the photoreceptor while scraping by a magnetic brush charging device that rotates and rubs the charging polarity (varies from minus to plus). Can be adjusted to a desired polarity.

Therefore, even in a magnetic brush charging device utilizing a so-called discharge phenomenon, a clear image can be formed without using an independent cleaner device by utilizing frictional charging between the magnetic particles constituting the discharge or the magnetic brush and the toner. Becomes

Furthermore, even when a contact injection charging method that does not use a discharge phenomenon is used, the independent polarity is controlled by using the frictional charging of the magnetic particles and the toner remaining after the transfer to control the desired polarity. Clear images can be formed without the need.

That is, in the magnetic particles for charging used in the cleanerless system, the frictional charging of the toner with respect to the contact between the magnetic particles is controlled and maintained, and the photosensitive member is charged to a predetermined potential. Function is required. The magnetic particles for charging are similar to carriers used in developers and the like, but have completely different required functions, and therefore have naturally different characteristics and configurations.

[0018]

As described above, the technology for reproducing magnetic particles for photoreceptor charging has not been sufficiently developed, and it is necessary to develop a technology for suitable reproduction.

Further, in the cleaner system, it is expected that the chance of contact between the magnetic particles for charging and the toner component is increased. Therefore, particularly in the cleanerless technology, the development of a suitable reproducing technology of the magnetic particles for charging is developed. Is urgently needed.

An object of the present invention is to provide a reusable magnetic particle suitable for use in charging an electrophotographic photoreceptor, and more specifically, to provide a suitable reproducing method of a charged magnetic particle after use. is there.

It is another object of the present invention to provide a charging magnetic particle reproduced by this method and an apparatus using the same.

[0022]

The present invention is characterized in that, after using magnetic particles for charging used in an apparatus for charging an electrophotographic photosensitive member to a predetermined potential, attached matter is washed and removed with a solvent. The present invention relates to a charging magnetic particle reproduced by the method and an apparatus using the same.

According to the present invention, the magnetic material having a reduced charging property of the photoreceptor due to a deposit (so-called contamination or spent) caused by being used for charging the photoreceptor is recovered, and the deposit is washed and removed with a solvent. Since the excellent photoreceptor charging characteristics can be recovered by the simple method described above, an excellent method for reproducing magnetic particles for charging can be provided.
Therefore, by performing the regenerating treatment of the used magnetic particles for charging by the regenerating method of the present invention, it is possible to obtain magnetic particles that can be repeatedly used and an apparatus using the same.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION When magnetic particles are used for charging, the components of the adhered substance on the surface are mainly composed of a substance derived from a toner component and a substance derived from a photoreceptor component. It has various molecular weight distributions including a solvent-soluble component and an insoluble gel component, and additives (consisting of a solvent-soluble component and an insoluble component).
In consideration of the above, a better effect can be obtained by selecting a solvent which can easily dissolve and swell them, and usually a solvent having a high polarity can be obtained. Further, in the present invention, especially when various kinds of deposit components are mixed or the degree of spent is large,
It is possible to select various cleaning forms, such as repeating cleaning several times, selecting several kinds of solvents having different SP values, and cleaning sequentially or mixing and then cleaning. According to the study of the present inventors, good results were obtained when aromatic compounds and ketones were used among various solvents, but among them, particularly excellent results were obtained when toluene was used. Therefore, for simplification, it is preferable to select toluene in advance as a standard solvent.

Further, it is more effective if free spent components are removed in advance by a suitable method such as washing with water, air blow or a sieve before the solvent washing. Further, it is preferable to apply a physical force such as ultrasonic vibration (oscillation frequency is preferably 10 kHz or more), stirring, flow, etc. at the time of solvent washing, and to heat the solvent appropriately or use solvent vapor. By doing so, it is possible to obtain a further effect.

Furthermore, in the present invention, the magnetic particle surface has a coupling agent having at least one central element selected from the group consisting of titanium, silicon, aluminum and zirconium and an alkyl chain having 6 or more carbon atoms. The coupling agent is preferably present in an amount of 0.0001% by mass or more and 0.5% by mass or less based on 100 parts by mass of the magnetic particles for the following reason.

First, since the surface of the magnetic particles is treated with a coupling agent, not only the excellent solvent resistance of the coupling agent itself but also a strong adhesion force due to a strong chemical bond between the coupling agent and the substrate. The influence of the solvent on the surface of the magnetic particles such as peeling or dissolution of the coat layer due to the solvent washing is eliminated.
Therefore, there is an advantage that excellent effects can be obtained by a simple method since the selection range of the solvent can be expanded without being restricted by the cleaning solvent.

Second, since the surface of the magnetic particles is treated with a coupling agent, lubricity is imparted by the long-chain alkyl group contained in the coupling agent, thereby reducing the surface contamination of the charging magnetic particles themselves. At the same time, it is possible to simultaneously obtain the effect of promoting the detachment of the deposit components during the solvent washing. In particular, in a cleanerless system having no independent cleaner mechanism, since there are many opportunities for the transfer residual toner to contact the magnetic particles, the adhesion of the magnetic particles to the stain tends to be promoted. Therefore, the present invention is particularly suitable for magnetic particles for charging used in a cleanerless system, and is not limited to a charging method (discharge charging or injection charging), but is most suitable for an injection charging method which is easily affected by spent. is there.

In order to obtain the above effects favorably, the amount of the coupling agent is preferably 0.0001% by mass or more and 0.5% by mass or less, more preferably 100% by mass of the magnetic particles for charging. Is 0.001% by mass or more and 0.2
% By mass or less. The amount of the coupling agent is 0.00
If the amount is less than 01% by mass, the adhesion strength to the substrate may be reduced, and the coating layer may be damaged during solvent washing, so that careful attention to the processing conditions may be required. In addition, since the releasing effect tends to be small, the rate of adhesion of the adhered substance during use may be increased, or it may take time to wash away the adhered substance with a solvent. on the other hand,
If the amount of the coupling agent is more than 0.5% by mass, the amount of free components not involved in the adhesion to the base material increases, so that the free components and the attached components tend to be firmly fixed and are difficult to remove by solvent washing. Because of this, processing may still take time. In order to measure the abundance of the coupling agent, there is a method in which the loss on heating is determined using a thermobalance or the like, and this value is used as the abundance.

Further, the reaction rate of the coupling agent is 80
% Or more, more preferably 85%
That is all. This is because if the proportion of unreacted substances is large, the coating layer is likely to be damaged during solvent washing.

However, even if the magnetic particles are washed by the method of the present invention, a small amount of deposits may actually remain on the surface of the magnetic particles depending on the conditions and methods (hereinafter referred to as residual deposits). is there. According to the study of the present inventors, the residual adhesion amount is 0.5% by mass or less based on 100 parts by mass of the magnetic particles,
When the content is preferably 0.3% by mass or less, excellent characteristics as magnetic particles for charging can be secured and recovered. When the surface of the magnetic particles after washing is observed with an electron microscope, it can be seen that the adhered substance has been removed and the surface of the magnetic particles has appeared, and has almost recovered to the state before use. To measure the amount of residual deposits, in a solvent that best dissolves and swells the deposits,
There is a method in which the magnetic particles for charging after washing are immersed, and the magnetic particles are obtained from the weight difference between the magnetic particles before and after the immersion, and a method in which the particles are obtained from the weight loss by heating using a thermobalance. When a solvent is used, toluene is generally used, but more preferably, for example, several kinds of solvents having different SP values are used.

By appropriately selecting these methods and conditions, a very simple and effective reproducing method can be realized. However, the magnetic particles of the present invention are not suitable for maintaining stable charging characteristics. Its average particle size is 5 μm
It is preferable that the particle size distribution is not less than 100 μm, and the particle size distribution has two or more peaks or shoulders in the range of 0.1 μm or more and 200 μm or less, and preferably the peak or shoulder of the particle size distribution is 0.5 μm or more and 30 μm or less, and 10 μm
It is desirable that the thickness be in the range of at least 100 μm.

Further, the present invention provides a magnetic particle for charging, characterized in that magnetic particles having an average particle size equal to or less than the average particle size are mixed with the magnetic particles obtained by removing the deposits by solvent washing. , A regenerated magnetic particle for charging, and an apparatus using the same. For example, the average particle size of the collected and washed magnetic particles used for charging the photoreceptor tends to be larger than the average particle size before use. The reason for this is unknown, but the component (small powder) having a small particle size is substantially small in magnetic force and weight.
For example, when a shock that exceeds the range normally conceivable at the time of collection and transfer is applied, or when washing is performed with a solvent, the fine powder component is lost, and the average particle diameter is increased as a whole by that amount. Presumed. As described above, from the viewpoint of maintaining stable charging characteristics, the initial average particle size,
It is preferable to adjust the particle size distribution. As the average particle diameter after adjustment, the average particle diameter of the magnetic particles before the n-th use is D
The average particle size before the {n}, {n + 1} th use is D {n +
When 1｝ and n are integers of 1 or more, D {n + 1} is D
It is desirable that the value (D {n + 1} / D {n}) divided by {n} has a relationship of 0.8 ≦ D {n + 1} / D {n} ≦ 1.2. 0.9 ≦ D {n + 1} / D {n} ≦ 1.1.

In order to satisfy this relationship, a predetermined amount of magnetic particles having an average particle diameter smaller than the average particle diameter of the magnetic particles after the solvent washing may be mixed. Further, if the average particle size after solvent washing is included in this range, it may be used as it is,
In order to further approach the initial value, a predetermined amount of magnetic particles having an average particle size smaller than the average particle size of the magnetic particles after the solvent washing may be mixed. The addition amount of the magnetic particles having an average particle size smaller than the average particle size of the magnetic particles after the solvent washing may be added in an appropriate amount according to the average particle size after the solvent washing, and it may be an unused product or a washed product. Needless to say.

The average particle size was measured using a laser diffraction type particle size distribution analyzer HEROS (manufactured by JEOL Ltd.).
２００200 μm is divided into 32 logarithms and measured to obtain a volume of 5
The average particle size was defined as the 0% average particle size. In addition, the average particle diameter of the whole may be obtained by randomly extracting 100 or more particles by an optical microscope or a scanning electron microscope, and using the maximum horizontal chord length as the particle diameter.

By the way, the magnetic particles obtained by the present invention can secure excellent properties as magnetic particles for charging, but when they are repeatedly used as magnetic particles for a magnetic brush charging device, as described above, It is used in various forms such as mixing several types of magnetic particles. For example, when several types of magnetic particles are mixed and used repeatedly, the amount of residual deposit on each magnetic particle may be different. In this case, the value obtained by measuring the amount of residual deposits of the mixed magnetic particles can be regarded as the average value of the amount of residual deposits of the respective magnetic particles. Expressed as the average amount of residual deposits. In other words, the average residual deposit amount is the residual deposit amount immediately before repeated use as a magnetic brush charging device. Naturally, when used directly after cleaning, the residual deposit amount corresponds to the average residual deposit amount. I do. In the present invention, in order to exhibit desired characteristics as a magnetic brush charging device, the average amount of residual deposits is preferably 0.5% by mass or less, more preferably 0.3% by mass, based on 100 parts by mass of the magnetic particles. % Or less.

As described above, the magnetic particles in the present invention are:
It is composed of at least a substrate and a coupling agent,
Known substrates such as ferrite and magnetite produced by various production methods can be used as the substrate, and additives such as phosphorus may be added as necessary.

On the other hand, the coupling agent is a compound having a hydrolyzable group and a hydrophobic group composed of a long-chain alkyl in the same molecule and bonded to a central element such as silicon, aluminum, titanium and zirconium. is there. As the hydrophobic group portion, a configuration in which carbon atoms are 6 or more, preferably 8 or more, and more preferably a linear chain is suitable. However, when the number of carbon atoms exceeds 30, it is generally difficult to dissolve in a solvent. In order to obtain a uniform coating state, additional means such as heating may be required. In the form of bonding with the central element, carboxylic acid ester, alkoxy, sulfonic acid ester, phosphoric acid ester, or direct bonding may be used. Further, the structure may contain a functional group such as an ether bond, an epoxy group or an amino group. As the hydrolyzable group, for example, an alkoxy group such as a methoxy group, an ethoxy group, a propoxy group and a butoxy group, which is relatively hydrophilic, is used. In addition, an acryloxy group, a methacryloxy group, a halogenated product thereof, and the like can also be used. Here, as a method for measuring the reaction rate of the coupling agent, a solvent capable of dissolving the coupling agent to be used may be selected, and the abundance before and after washing may be measured. For example, a means for immersing in a solvent 100 times the amount of the treated magnetic particles and quantifying the coupling agent component in the solvent by chromatography, and a coupling agent component remaining on the surface of the magnetic particles after washing is ESCA, CHN and TGA
For example, means for quantifying the amount before and after washing, and the like can be used.

The charging magnetic particles used in the present invention have a volume resistance of 1 × 10 ⁴ Ωcm or more and 1 × 10 ⁹ Ωcm or more.
It is preferably Ωcm or less. If it is lower than 1 × 10 ⁴ Ωcm, pinhole leakage tends to occur, and
If it exceeds 10 ⁹ Ωcm, the charging of the photoreceptor becomes insufficient. However, the amount of the coupling agent of the magnetic particles for charging of the present invention is 0.0001% by mass or more and 0.5% by mass or less. Since it is preferably 0.001% by mass or more and 0.2% by mass or less, the resistance value is substantially the same as the resistance value of the magnetic particles not present on the surface, that is, the substrate itself. The production stability and the quality stability are higher than in the case of using a conductive particle-dispersed resin. Therefore, it is preferable to optimally adjust the resistance value of the substrate within the preferable range of the resistance value as the magnetic particles. To this end, the composition and the crystal structure of the substrate are adjusted by optimizing the production conditions such as raw materials and firing conditions. You just need to adjust things like that.

FIG. 3 shows a method of measuring the volume resistance. Cell 3
0 is filled with magnetic particles, and the electrode 3 is contacted with the magnetic particles.
1 and 32 were arranged, a voltage was applied between the electrodes, and the current flowing at that time was measured. The measurement conditions were 23 ° C,
Contact area between filled magnetic particles and electrodes in an environment of 65% humidity 2
cm ² , thickness 1 mm, 10 kg for upper electrode, applied voltage 1
00V.

An apparatus using the magnetic particles for charging of the present invention is
Therefore, conventionally known photoreceptors are used,
In particular, when using the injection charging method as the charging method
Forms a charge injection layer on the surface of the photoreceptor. Its volume resistance
The resistance value is 1 × 10⁸ ~ 1 × 10 ^FifteenΩcm range
However, preferably, 1 × 10^Ten~ 1
× 10^FifteenΩcm, more preferably considering environmental fluctuations
Then 1 × 10¹²~ 1 × 10 ^FifteenΩcm. Charge injection layer
The method of measuring the volume resistivity of
Charge injection layer on ethylene terephthalate (PET)
Create a volume resistance measurement device (Hewlett-Packard)
23 ° C., 4140B
Apply 100V voltage in 65% environment and measure
No.

As the charge injection layer, a method in which a light-transmissive and conductive particle is dispersed in an insulating binder resin in an appropriate amount and made of a material adjusted to the above resistance range, or an inorganic layer having the above resistance is used. It is selected according to the purpose from various methods such as a forming method.

As a first method, for example, when a charge injection layer is formed using a material in which a light-transmissive and conductive particle is dispersed in an appropriate amount in an insulating binder resin, It can be used by selecting from known materials,
Further, as the conductive particles, the particle size is preferably 0.3 μm or less from the viewpoint of light transmission, and most preferably 0.1 μm.
m or less. 2 to 25 based on 100 parts by mass of binder resin
0 parts by mass, preferably 2 to 190 parts by mass. If the amount is less than 2 parts by mass, it is difficult to obtain a preferable volume resistance value.
If it exceeds 50 parts by mass, the film strength tends to decrease, and the charge injection layer tends to be scraped. The thickness of the charge injection layer is preferably 0.1 to 10 μm, and most preferably 1 to 7 μm.
It is.

Furthermore, lubricant particles may be contained in the charge injection layer for improving the charging characteristics and the releasability. As the lubricant particles, it is preferable to use a fluororesin, a silicone resin or a polyolefin resin having a low critical surface tension, and among them, a polyethylene tetrafluoride resin is most preferable. In this case, the amount of the lubricating powder to be added is preferably
2 to 50 parts by mass relative to 0 parts by mass, more preferably 5 to 50 parts by mass
40 parts by mass.

As a second method, for example, when an inorganic layer is formed as a charge injection layer, the underlying photoconductive layer is preferably made of amorphous silicon, and a blocking layer and a photoconductive layer are formed on a cylinder by glow discharge or the like. Preferably, a layer and a charge injection layer are formed sequentially.

As the photosensitive material, conventionally known materials can be used. For example, if it is an organic material, a phthalocyanine pigment, an azo pigment, or the like may be used. Further, an intermediate layer may be provided between the surface protective layer and the photosensitive layer. The purpose of such an intermediate layer is to enhance the adhesion between the protective layer and the photosensitive layer, or to function as a charge barrier layer. As the intermediate layer, for example, a commercially available resin material such as an epoxy resin, a polyester resin, a polyamide resin, a polystyrene resin, an acrylic resin, and a silicone resin can be used. As a conductive support for the photoconductor, metals such as aluminum, nickel, stainless steel and steel,
Plastic or glass having a conductive film, conductive paper, or the like can be used.

The toner used in the present invention is not particularly limited, but has a preferable range in terms of triboelectric charging between the magnetic particles of the present invention and the toner used. At a ratio of 7 parts by mass of the toner used to 100 parts by mass of the magnetic particles for charging, the measured tribo value of the toner is the same as the charging polarity of the photoconductor and is in the range of 10 to 40 mC / Kg. This is good for the characteristics of taking in, sweeping out toner, and charging the photosensitive member. Further, from the viewpoint of improving the transfer efficiency, there is also a preferred form as a toner. In other words, the smaller the amount of toner remaining after transfer, the smaller the amount of toner mixed in the magnetic brush, so that the amount of spent magnetic particles can be reduced and the effect of the present invention can be further improved. Although conventionally used as an index indicating the form of the toner, the shape factor: SF-1 is 100 to 140, and S
Those having F-2 in the range of 100 to 120 are preferred.

Here, for SF-1 and SF-2,
It is measured as follows.

For example, FE-SEM (S-
800), 100 toner images of 2 μm or more, which are enlarged 1000 times, are randomly sampled, and the image information is introduced into, for example, an image analyzer (LuzexIII) manufactured by Nicole Co. via an interface and analyzed to obtain the following equation. Defined value.

[0050]

(Equation 1)

[0051]

(Equation 2)

Here, MXLNG represents the absolute maximum length of the particle, PERIME represents the peripheral length of the particle, and AREA represents the projection surface of the particle. SF-1 indicates the degree of roundness of the particles,
SF-2 indicates the degree of unevenness of the particles.

The structure of the magnetic brush charging device using the magnetic particles for charging according to the present invention is as follows.
A magnet roll or a conductive sleeve having a magnet roll inside and coated with magnetic particles uniformly is preferably used.

The amount of the magnetic particles for charging held by the magnetic particle holding member for charging is preferably 50 to 500 mg / cm.
² , more preferably 100 to 300 mg / cm ² to obtain stable charging properties. Further, extra charging magnetic particles may be held in the charging device and circulated.

The magnetic brush may be moved in the opposite direction with respect to the method of moving the photoreceptor at the contact portion, but may move in the opposite direction from the viewpoint of taking in the residual toner after transfer. preferable.

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited by these examples.

[0057]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the structure, material, manufacturing method, and the like of members and an evaluation machine used in the present invention will be described. [Production Example 1 of Charging Magnetic Particles] Zn— having an average particle diameter of 40 μm
Cu ferrite particles (addition of 0.5 parts by mass of phosphorus to 100 parts by mass of ferrite) and Zn-Cu having an average particle size of 15 μm
Ferrite particles (addition of 0.5 parts by mass of phosphorus to 100 parts by mass of ferrite) were mixed at a mass ratio of 1: 0.5, and an average particle size of 30 μm having a peak at each average particle size position.
m of ferrite particles were produced. This volume resistance is 4 × 1
At 0 ⁷ Ωcm, the magnetization at 8 × 10 ⁴ A / m (1 KOe) was 57 Am ² / kg (57 emu / g).

The volume resistance of the ferrite particles is shown in FIG.
The following procedure was performed using the apparatus shown in (1). The cell 30 was filled with ferrite particles, electrodes 31 and 32 were arranged so as to be in contact with the ferrite particles, a voltage was applied between the electrodes, and the current at that time was measured. Measurement conditions are 23
Contact area between filled particles and electrodes in an environment of 65 ° C and 65% humidity 2
cm ² , thickness 1 mm, 10 kg for upper electrode, applied voltage 1
00V.

The average particle size was measured using a laser diffraction type particle size distribution analyzer HEROS (manufactured by JEOL Ltd.).
２００200 μm is divided into 32 logarithms and measured to obtain a volume of 5
The average particle size was defined as the 0% average particle size.

Next, a titanium coupling agent (isopropo
0.05 parts by weight of xylene titanium tristearate)
Dissolved in 50 parts by mass of titanium coupling agent solution.
Made. 100 parts by mass of the above ferrite particles are added thereto.
After maintaining the temperature at 80 ° C. while stirring and evaporating the solvent,
Place in a 200 ° C oven, cure and charge
Magnetic particles No. 1 was created. The magnetic particles for charging
The volume resistance of 1 is 5 × 10 ⁷ Ωcm, average particle size is 30μ
m, the peak position exists at two places of 15 μm and 40 μm.
I was These are the same conditions as when the above ferrite is used.
The measurement was performed on the subject.

Further, the amount of the coupling agent was measured. The measurement was performed using a thermobalance (TGA 7 thermogravimetric analyzer, manufactured by PerkinElmer) to determine the weight loss on heating, and this value was used as the abundance. More specifically, the amount of mass reduction when 50 mg of a sample (magnetic particle No. 1 for charging in this embodiment) was changed from 150 ° C. to 800 ° C. (rise rate was 25 ° C./min) in a nitrogen atmosphere. Was regarded as the weight loss on heating. Table 1 shows the characteristics
Put together.

[Production Example 2 of Magnetic Particles for Charging] The ferrite particles obtained in Production Example 1 of Magnetic Particles for Charging were used as they were,
The magnetic particles for charging And 2. The characteristics are summarized in Table 1.

[Production Examples 3 to 8 of Magnetic Particles for Charging] The amounts of the titanium coupling agent (isopropoxytitanium tristearate) were 0.0001 part by mass, 0.001 part by mass, 0.1 part by mass and 0.1 part by mass, respectively. 2 parts by mass, 0.5 parts by mass, 1.
Except for using 0 parts by mass, the same procedure as in Production Example 1 of charging magnetic particles was performed. 3, No. 4, N
o. 5, no. 6, no. 7, no. 8 was obtained. The characteristics are summarized in Table 1.

[Production Example 9 of Charging Magnetic Particles] A solution was prepared by dissolving in a silane coupling agent, 0.05 parts by mass of dodecyltrimethoxysilane and 30 parts by mass of methyl ethyl ketone. 100 parts by mass of the obtained ferrite particles were added, and kept at 70 ° C. while stirring, and after evaporating the solvent, put in an oven at 150 ° C.,
After curing, the charging magnetic particles 9 was obtained.
The characteristics are summarized in Table 1.

[Production Example 10 of Magnetic Particles for Charging] Average particle size 3
0 μm Mn—Mg ferrite particles (Ferrite 100
Charging magnetic particles No. 1 except that 0.5 parts by mass of phosphorus was added to parts by mass). 10 was obtained. The characteristics are summarized in Table 1.

[Production Example 11 of Charging Magnetic Particles]
5 μm Zn—Cu ferrite particles (Ferrite 100
Charging magnetic particles No. 1 except that 0.5 parts by mass of phosphorus was added to parts by mass). 11 was obtained. The characteristics are summarized in Table 1.

Production Example 12 of Magnetic Particles for Charging The ferrite particles obtained in Production Example 11 of magnetic particles for charging were used as they were, It was set to 12. The characteristics are summarized in Table 1.

[Production Examples 13 to 18 of Charging Magnetic Particles] Production of charging magnetic particles except that Zn—Cu ferrite particles having an average particle diameter of 15 μm (0.5 parts by mass of phosphorus was added to 100 parts by mass of ferrite) were used. In the same manner as in Examples 3 to 8, the magnetic particles No. 13, No. 14, No. 15, N
o. 16, No. 17, No. 18 was obtained. Table 1 shows the characteristics
Put together.

[Photoreceptor Production Example 1] On a 30 mm-diameter aluminum cylinder, a functional layer is provided in the order of an undercoat layer, a positive charge injection preventing layer, a charge generation layer, and a charge transport layer.

The undercoat layer is a conductive layer having a thickness of about 20 μm provided to smooth out defects of the aluminum drum and to prevent the occurrence of moire due to the reflection of light exposure.

The positive charge injection preventing layer is provided to prevent the positive charge injected from the aluminum support from canceling out the negative charge charged on the surface of the photoreceptor, and is formed of a polyamide resin having a thickness of about 1 μm to form a 10 ⁶ Ωcm. The resistance is adjusted to the extent.

The charge generation layer is a layer provided to generate positive and negative charge pairs by receiving laser exposure, and is a layer having a thickness of about 0.3 μm in which a titanyl phthalocyanine pigment is dispersed in a resin. The charge transport layer is a 17 μm-thick layer in which hydrazone is dispersed in a polycarbonate resin, and is a P-type semiconductor. Therefore, the negative charges charged on the photoreceptor surface cannot move through this layer, and only the positive charges generated in the charge generation layer can be transported to the photoreceptor surface.

When the surface resistance of the photoreceptor was measured, it was 5 × 10 ¹⁵ Ωcm for the charge transport layer alone.

Further, a charge injection layer was formed thereon, and 1 was obtained. The charge injection layer is composed of 100 parts by mass of a photocurable acrylic resin, antimony-doped SnO ₂ ultrafine particles 15 having a particle diameter of about 0.03 μm and having a low resistance.
0 parts by mass, 18 parts by mass of tetrafluoroethylene resin particles, and 1.5 parts by mass of a dispersant are dispersed.

The surface resistance of the photosensitive member at this time was 3.3 × 10
It was ¹³ Ωcm.

[Toner Production Example 1] 90 parts by mass of styrene
10 parts by mass of n-butyl acrylate, 5 parts by mass of low molecular weight polypropylene, 5 parts by mass of carbon black, 1.5 parts by mass of a metal-containing azo dye, and 3 parts by mass of an azo initiator are dispersed and mixed. Next, 500 parts by mass of a dispersion having a ratio of 1 part by mass of calcium phosphate to 100 parts by mass of pure water was prepared, and the dispersion mixture was added thereto, dispersed well by a homomixer, and polymerized at 80 ° C. for 10 hours. The obtained polymer was filtered, washed, and dried and classified to obtain a toner composition.

To the above toner composition, 2.5 mass% of hydrophobically treated titanium oxide was externally added, and the mass average diameter was 7.3 μm.
Of toner No. 1 was created.

This toner is formed into a spherical shape by a polymerization method. The shape factors were 114 for SF-1 and 105 for SF-2.

[Toner Production Example 2] 100 parts by mass of a polyester resin 2 parts by mass of a metal-containing azo dye 2 parts by mass of a low molecular weight polypropylene 4 parts by mass 6 parts by mass of a carbon black After the above materials were dry-mixed, a biaxial kneading extruder set at 160 ° C. And kneaded. Cool the obtained kneaded material,
After finely pulverized by an air-flow type pulverizer, the particles were classified by wind power to obtain a toner composition having a controlled particle size distribution. To this toner composition, 1.4% by mass of hydrophobically treated titanium oxide was externally added to form a toner having a mass average particle size of 7.1 μm. 2 was created.

[Developer Production Example 1] A toner obtained by coating nickel-zinc ferrite having an average diameter of 60 μm with an acryl-modified silicone resin was added to 100 parts by mass of toner No. 1
Was mixed with 6 parts by mass of developer No. It was set to 1.

[Developer Production Example 2] A toner obtained by coating nickel zinc ferrite having an average diameter of 60 μm with a silicone resin was added to 100 parts by mass of toner No. 2 and 6 parts by mass of developer No. 2 were mixed. And 2.

[Digital Copier] An electrophotographic apparatus as an evaluation machine used in Examples and Comparative Examples of the present invention was prepared as follows. First, a digital copying machine using a laser beam as an electrophotographic apparatus (Canon: G
P55) 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 charger, cleaning means, and photosensitive member are an integrated unit. The process speed is 150 mm / s. The digital copier was modified as follows.

First, the process speed was set to 200 mm / s
And

From the one-component jumping development,
Modifications were made to make the two-component developer usable. Furthermore, a diameter 16 with a magnet roller included in the charged part
mm conductive non-magnetic sleeve is provided to form a charging magnetic brush. Further, the transfer means using a corona charger was changed to a roller transfer method, and the pre-charge exposure means was removed.

The gap between the conductive sleeve of the charged portion and the photosensitive member was set to 0.5 mm.

As for the developing bias, a rectangular wave of 1000 Vpp / 3 kHz is superimposed on a DC component of -500 V.

Further, the cleaning blade was removed to obtain a cleanerless copying machine (digital copying machine No.
1). FIG. 1 shows a schematic diagram.

Next, the present invention will be described with reference to Examples and Comparative Examples using these members and devices.

Example 1 Charging Magnetic Particles 1 to 5
0 g and the coating density is 180 mg / cm
Adjusted to ² to prepare a magnetic brush charging device. An injection charging method using this charging device is adopted, and the digital copying machine No. The durability test was performed on the sample No. 1 under the following conditions.
Other combinations are shown in Table 2.

Evaluation mode: 3% character original, A4 landscape feed,
Continuous paper supply Applied bias to charging device: DC voltage -700 V and 1
kHz, 700 Vpp rectangular wave AC component Endurance environment: 25 ° C./relative humidity 60% Endurance test was conducted while supplying and replacing toner and other consumables as needed.
Good images were obtained up to one sheet. When the charging potential convergence was measured, the initial value was 98%, and after 100,000 sheets, 95%.
Met. After that, when the endurance was resumed, a slight fog occurred soon. The charge potential convergence at this time is 83%
Met.

The charge potential convergence in the present invention is an index indicating charge stability, and is the ratio of the photosensitive member charge potential (V _D ) to the applied DC voltage (V _DC ), ie, | V _D | × 100 / | V _DC | (%). In the present invention, a DC voltage of -700 V and 1 kHz, 7
Since a rectangular wave AC component of 00 Vpp is applied, it indicates what percentage of the DC component, -700 V, reaches the charged potential of the photoconductor.

Here, the durability was ended, the charging device was disassembled, and the magnetic particles were recovered. The collected magnetic particles were air blown to remove a mixture such as free toner, and then washed with toluene. The washing conditions are as follows. 200 ml of toluene per 10 g of collected magnetic particles (including adhering matter and mixture)
The magnetic particles are immersed in toluene at a ratio of
Ultrasonic wave (oscillation frequency 47kHz)
z) for 15 minutes. Thereafter, the magnetic particles were separated from toluene, air-dried, and completely dried while stirring in a 200 ° C. oven. 1 was obtained. The measured average particle size was 36 μm.

Further, the amount of remaining deposits was measured according to the following procedure. First, the magnetic particles No. 1 is accurately weighed to 1 g (to the order of 0.1 mg), and is defined as Wb.
Next, 20 ml each of toluene, acetone and carbon tetrachloride is placed in a beaker. Magnetic particles for recharging no. 1
Is immersed in toluene, and the whole container is placed in a water tank kept at 50 ° C. in advance and irradiated with ultrasonic waves for 15 minutes. Then, after changing the solvent in the order of acetone and carbon tetrachloride and performing the same treatment, the magnetic particles were separated, air-dried for one day, dried in an oven at 200 ° C. for 5 hours, and cooled in a desiccator. The weight of the magnetic particles is measured (Wa) and calculated by the following equation.

Residual deposit amount (% by mass) = (Wb-Wa)
× 100 / W a. 1 had a residual deposit amount of 0.18% by mass.

Here, the magnetic particles No. No. 1 and the magnetic particles for charging No. 1 11 were mixed so that the mass ratio became 3: 1. 101 was obtained. The magnetic particles for charging The average particle size of 101 was 31 μm.
That is, in the case of the present embodiment, the value of D {n + 1} is equal to the magnetic particle No. for charging. 101 is the average particle diameter, and the value of D {n} is the magnetic particle for charging. D ｛n
+1｝ = 31 and D {n} = 30. Therefore, D ｛n
+ 1 / D {n} = 1.03.

Next, the charging magnetic particles No. The measurement of the average amount of the remaining deposits of No. 101 was performed using the magnetic particles No. 1 for charging after washing.
The same method as that used for determining the amount of residual deposits of No. 1 yielded 0.13% by mass.

Further, the magnetic particles for charging no. The amount of the coupling agent present in 101 was measured. As in this case, when the weight loss due to heating is measured with a thermobalance in the presence of the attached matter, the value calculated as the weight loss due to heating is measured as a value to which the attached matter is added. Therefore, in the present invention, the value obtained by subtracting the average amount of deposits in the present invention from the loss on heating in the present invention is defined as the amount of the coupling agent present in the charging magnetic particles including the recycled product.
The measurement method, conditions, and the like are set as follows. 1 was measured in the same manner as in measuring the abundance of the coupling agent in No. 1. In 101, the amount of the coupling agent was 0.05% by mass. (Note that
This procedure may be followed when several types of magnetic particles having different amounts of the coupling agent are mixed. In addition, the volume resistance was 6 × 10 ⁷ Ωcm.

Thereafter, the charging magnetic particles No. 101, using the magnetic particles for charging No. 101; Under the same conditions as the durability test performed using No. 1, durability was repeated up to 100,000 sheets, and the image and potential convergence were checked every 20,000 sheets.
The results are summarized in Table 3.

[Examples 2 to 14] Evaluations and measurements were performed in the same manner as in Example 1 using combinations shown in Table 2.

In this embodiment, the charging magnetic particles are changed. The results are summarized in Table 3.

[Examples 15 and 16] Evaluation and measurement were performed in the same manner as in Example 1 by using combinations shown in Table 2.

In this embodiment, the cleaning solvent is changed.
The results are summarized in Table 3.

Example 17 Evaluation and measurement were performed in the same manner as in Example 1 by using the combinations shown in Table 2. Table 3 shows the results.

[Comparative Example 1] Evaluation and measurement were performed in the same manner as in Example 1 using combinations shown in Table 2.

In this comparative example, the washing was performed with water.
Fog occurred from the beginning during repeated use. It was found that almost no extraneous matter was removed, and it was not suitable as a regeneration method. Table 3 shows the results.

Comparative Example 2 Evaluation and measurement were performed in the same manner as in Example 1 using combinations shown in Table 2.

In this comparative example, the deposits were removed by heating. The heating conditions are from 150 ° C. to 80 ° C. in a nitrogen atmosphere.
The temperature is 0 ° C. (rise rate is 25 ° C./min), which is sufficiently lower than the firing temperature of ferrite (generally, about 1300 ° C.). After heating, it was cooled in a nitrogen atmosphere. Then, after air blowing, washing with toluene and drying to remove free matter revealed that the coupling agent had disappeared, which was clearly different from the first use condition. Therefore, it is not appropriate as a reproducing method. Table 3 shows the results.

[Comparative Examples 3 and 4] Evaluations and measurements were performed in the same manner as in Example 1 using combinations shown in Table 2.

In this comparative example, the deposits were removed by heating.
The heating conditions are a temperature of 400 ° C. in air for 1 hour and 2 hours. After cooling, air blowing, washing with toluene,
After drying to remove free matter, the resistance was measured.
× 10 ⁹ Ωcm, and fog occurred from the beginning when used repeatedly. It was found that the characteristics were clearly different from those in the first use. Therefore, it is not appropriate as a reproducing method. Table 3 shows the results.

[0110]

[Table 1]

[0111]

[Table 2]

[0112]

[Table 3]

[0113]

[Table 4]

[0114]

As described above, according to the present invention, excellent charging characteristics can be recovered by simple means, so that an excellent method for reproducing magnetic particles for charging can be obtained. Further, according to the reproducing method of the present invention, it is possible to provide a charging magnetic particle having good charging characteristics over a long period of time and being reusable, and a device using the same.

[Brief description of the drawings]

FIG. 1 is an example of an electrophotographic apparatus using the magnetic particles of the present invention.

FIG. 2 is another example of an electrophotographic apparatus using the magnetic particles of the present invention.

FIG. 3 is a schematic diagram of measuring the volume resistance of the magnetic particles of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Photoreceptor 2 Magnetic brush charging device containing magnetic particles for charging of the present invention 21 Magnetic particles for charging of the present invention 22 Conductive sleeve containing magnet 3 Image exposure 4 Developing device 5 Transfer paper 6 Transfer device 7 Fixing device 8 Cleaning device 30 Measurement cell 31, 32 Electrode 33 Guide ring 34 Ammeter 35 Voltmeter 36 Constant voltage device 37 Measurement sample 38 Insulator

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshio Takamori 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Fumihiro Arahira 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inside the corporation

Claims (26)

[Claims] An apparatus for charging an electrophotographic photoreceptor to a predetermined potential, comprising: using magnetic particles for charging used in an apparatus for charging the electrophotographic photoreceptor to a predetermined potential; Of regenerating magnetic particles for charging. 2. The method for regenerating magnetic particles for charging according to claim 1, wherein ultrasonic vibration is applied during washing with a solvent. 3. The method for reproducing magnetic particles for charging according to claim 2, wherein the oscillation frequency of the ultrasonic wave is 10 kHz or more. 4. The method for regenerating magnetic particles for charging according to claim 1, wherein the solvent used for washing contains one or both of an aromatic compound and a ketone. 5. The method for regenerating magnetic particles for charging according to claim 4, wherein the aromatic compound is toluene. 6. The method for regenerating magnetic particles for charging according to claim 1, wherein the surface of the magnetic particles for charging is treated with a coupling agent. 7. The method for regenerating magnetic particles for charging according to claim 6, wherein the coupling agent has an alkyl chain having 6 or more carbon atoms. 8. The method according to claim 1, wherein the coupling agent is at least one selected from the group consisting of titanium, silicon, aluminum and zirconium.
The method for reproducing magnetic particles for charging according to claim 6, wherein the magnetic particles have two central elements. 9. The method according to claim 1, wherein the amount of the coupling agent is less than 1%.
The method for regenerating magnetic particles for charging according to any one of claims 6 to 8, wherein the amount is 0.0001% by mass or more and 0.5% by mass or less based on 00 parts by mass. 10. The magnetic particles for charging according to claim 1, wherein the magnetic particles after solvent washing and magnetic particles having an average particle size equal to or less than the average particle size are mixed. How to play. 11. A magnetic particle for charging used in an apparatus for charging an electrophotographic photoreceptor to a predetermined potential, wherein said magnetic particle has been processed by the reproducing method according to claim 1. Description: A regenerated magnetic particle for charging, characterized in that: 12. The regenerated magnetic particles for charging according to claim 11, wherein the amount of residual deposits after the solvent washing is 0.5% by mass or less based on 100 parts by mass of the magnetic particles. 13. The reproduced magnetic particles for charging according to claim 11, wherein the average particle diameter is 5 μm or more and 100 μm or less. 14. The particle size distribution is from 0.1 μm to 200 μm.
The regenerated magnetic particles for charging according to any one of claims 11 to 13, wherein the magnetic particles have two or more peaks or shoulders in the following ranges. 15. The regenerated magnetic particles for charging according to claim 11, wherein the reaction rate of the coupling agent is 80% or more. 16. The magnetic particles having a volume resistance of 1 × 10^Four 
Ωcm or more 1 × 10 ⁹ Ωcm or less
Regenerated charging according to any one of claims 11 to 15
For magnetic particles. 17. A charging device for charging an electrophotographic photoreceptor to a predetermined potential, wherein the charging device forms magnetic particles to which a voltage is applied in a brush shape, contacts the photoreceptor, and charges the photoreceptor. A magnetic brush charging device, wherein the magnetic particles are reproduced by the reproducing method according to any one of claims 1 to 10. 18. A magnetic brush charging device according to claim 17, wherein the regenerated magnetic particles for charging according to claim 11 are used as the magnetic particles. 19. The average particle size of the magnetic particles before the nth use is D {n}, and the average particle size before the {n + 1} th use is D
19. The magnetic brush charging device according to claim 17, wherein, when {n + 1}, 0.8 ≦ D {n + 1} / D {n} ≦ 1.2. (N is an integer of 1 or more) 20. The method according to claim 1, wherein the average amount of the remaining deposits is 100%.
20. The magnetic brush charging device according to claim 17, wherein the amount is 0.5% by mass or less based on parts by mass. 21. At least a charging step of charging a photoconductor by a charging device to which a voltage is applied, a step of forming an electrostatic latent image by image exposure, and a developing step of visualizing the electrostatic latent image with toner. An electrophotographic apparatus comprising: the magnetic brush charging device according to any one of claims 17 to 20 as the charging device. 22. The photoconductor has a photosensitive layer on a conductive support and a charge injection layer furthest from the conductive support, wherein the charge injection layer is at least 1 × 10 ⁸ Ωcm and at least 1 × 10 ⁸ Ωcm. ¹⁵ Ω
The electrophotographic apparatus according to claim 21, wherein the electrophotographic apparatus has a volume resistance value of not more than cm. 23. The electrophotographic apparatus according to claim 21, wherein the toner is produced by a polymerization method and has a spherical shape. 24. The electrophotographic apparatus has a transfer member for transferring a visualized electrostatic latent image to a transfer material, does not have an independent cleaning mechanism, and removes toner remaining on the photoreceptor after transfer. The electrophotographic apparatus according to any one of claims 21 to 23, wherein the electrophotographic apparatus is collected in a developing step. 25. A charging device, wherein at least one selected from the group consisting of an electrophotographic photosensitive member, a developing device, and a cleaning device is supported by one body, and the charging device is used as the charging device.
A process cartridge which is detachable from an electrophotographic apparatus, wherein the magnetic brush charging apparatus according to any one of the above items is used. 26. The process cartridge according to claim 21, wherein
26. The process cartridge according to claim 25, wherein the process cartridge is used in the electrophotographic apparatus according to any one of claims 24 to 24.