JP2001056598A - Magnetic particles for electrification, their production, electrifying member using same, image forming device and process cartridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain magnetic particles for electrification capable of preventing the scraping of a photoreceptor and excellent in electrifying cap ability and durability by using magnetic particles for electrification having a specified maximum chord length and a specified standard deviation in the minor to major axis length ratio. SOLUTION: The objective magnetic particles for electrification have magnetic particles, a 1st surface coating layer containing a 1st surface coating agent and coating the surface of each of the magnetic particles and a 2nd surface coating layer containing a 2nd surface coating agent and coating the surface of the 1st surface coating layer and comprise magnetic particles for electrification having >=5 μm maximum chord length and a standard deviation of >=0.08 in the minor to major axis length ratio. The image forming device has a magnetic brush electrifying device 202 having an electrically conductive sleeve 204 containing a magnet as a holding member and the magnetic particles 203 for electrification supported on the sleeve 204 by magnetic force as an electrifying member.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging magnetic particle for charging an image carrier used in a recording method using an electrophotography applied to a copying machine, a printer, a facsimile, and the like, and a method for producing the same. The invention also relates to a charging member, an image forming apparatus, and a process cartridge using the charging magnetic particles.

[0002]

2. Description of the Related Art Conventionally, many methods have been known as electrophotography. In general, a photoconductive substance is used to form an electric latent image on a photoconductor (image carrier) by various means. Formed, then develop the latent image with toner to form a visible image,
After transferring the toner image to a transfer material such as paper as necessary, the toner image is fixed on the transfer material by heat, pressure or the like to obtain a copy. 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 photoreceptor in such an electrophotographic method, there is a so-called corotron or scorotron charging method utilizing corona discharge. Furthermore, a charging method that minimized ozone generation was developed by bringing a charging member such as a roller, fur brush, or blade into contact with the surface of the photoreceptor, and discharging in a narrow space near the contact area. I have.

However, in a charging method using corona discharge, a large amount of ozone is generated during corona discharge, particularly when negative or positive corona is generated. Therefore, an electrophotographic apparatus is provided with a filter for capturing ozone. Therefore, there are problems such as an increase in the size of the apparatus and an increase in running costs. Further, in a system in which a charging member such as a blade or a roller is brought into contact with a photoconductor to perform charging,
There is a tendency for problems such as fusion of the toner on the photoreceptor to occur.

For this reason, a method of using the charging member only in proximity to the photosensitive member and avoiding direct contact has been studied. As the member for charging the photoconductor, the roller described above,
Examples of the member include a blade, a brush, and a member obtained by applying a resistance layer to a long and thin conductive plate. However, when charging is performed using each of these members, there is a problem that it is difficult to control the proximity distance between the charging member and the photosensitive member, and it has been difficult to put the member to practical use.

For this reason, a technique of using a so-called magnetic brush, which has a relatively small load due to contact with the photoreceptor and holds magnetic particles with a magnet, as a charging member, has been studied. As a charging method using magnetic particles, two methods have been proposed in combination with a photoreceptor. One is a method in which a charge injection layer is provided as a surface layer of a photoreceptor, and charges are directly injected to charge the photoreceptor through contact with the charge injection layer. The other is a method using a normal photoreceptor and utilizing the discharge of magnetic particles and minute voids on the surface of the photoreceptor.

As magnetic particles used as a charging member, JP-A-59-133569 discloses that iron powder is coated to adjust the resistance.
Japanese Patent No. 95115 discloses that a resin layer containing conductive particles is formed on the surface of magnetic particles to improve the environmental dependence of the resistance value and the reduction of magnetic particle surface contamination. Further, Japanese Unexamined Patent Application Publication No.
Japanese Patent Application Laid-Open No. 8-69149 proposes that the durability of a charging member is extended by mixing magnetic particles having a smooth surface and magnetic particles having an uneven surface. There is a disclosure that surface contamination of magnetic particles is prevented by using magnetic particles having a particle size distribution having a peak, and long-term charging stability is obtained.

There is also disclosed a technique for applying a magnetic brush charger to full-color image formation. For example, in JP-A-6-317969, one photoconductor is
There is disclosed an apparatus which includes yellow, cyan, magenta, and black developing units and charges a photosensitive member with a magnetic brush. However, there is no disclosure of preferred magnetic particles for color image formation.

As described above, there is a demand for the development of a more suitable configuration for magnetic particles as a charging member for charging a photoreceptor. In recent years, with the progress of image input / output, processing, and display technologies, simpler and lower-cost image hard copy / print technology has been demanded, and the unique problem of forming a full-color image using magnetic particles has also been addressed. There is a need for a solution.

[0010]

As described above, there is a need to develop magnetic particles for charging having a suitable structure as a charging member. That is, there is a need for magnetic particles that have stable charging properties when a charging device using magnetic particles for charging is continuously used and can withstand long-term use, a charging member using the same, an image forming apparatus, and a process cartridge. I have. In addition, even in full-color image formation, for a long time, magnetic particles that can obtain a clear image, a charging member using the same,
There is a demand for an image forming apparatus and a process cartridge.

It is an object of the present invention to provide a charging particle having excellent durability, a charging member using the same, an image forming apparatus, and a process cartridge. Another object of the present invention is to provide an image forming apparatus and a process cartridge in which the photoreceptor is hardly scraped.

Another object of the present invention is to provide a magnetic particle for charging capable of obtaining a clear image for a long time even in full-color image formation, a charging member using the same, an image forming apparatus, and a process cartridge. further,
SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing magnetic particles for charging, which is excellent in durability, has less abrasion of the photoreceptor, and can provide a stable full-color image for a long period of time.

[0013]

That is, the present invention relates to a magnetic particle for charging which charges an image carrier by rubbing against the image carrier on which an electrostatic latent image is formed. The particles include a magnetic particle, a first surface coating layer containing a first surface coating agent and covering the surface of the magnetic particles, and a second surface containing a second surface coating agent and covering the surface of the first surface coating layer. A magnetic layer for charging having a maximum chord length of 5 μm or more.
The standard deviation of the ratio of the minor axis length to the major axis length (minor axis length / major axis length) of the charging magnetic particles having the maximum chord length is 0.0.
The number of the magnetic particles is 8 or more.

The present invention also relates to a method for producing magnetic particles for charging which charges an image carrier by rubbing against the image carrier on which an electrostatic latent image is to be formed. Forming a first surface coating layer by coating the surface of the pulverized magnetic particles with a first surface coating agent, and coating the surface of the formed first surface coating layer with a second surface coating agent And a step of forming a second surface coating layer by the method.

According to the present invention, there is provided a charging member for charging an image carrier by rubbing against the image carrier on which an electrostatic latent image is formed, wherein the charging member is provided on a magnet having a conductor to which a voltage is applied. And the magnetic particles for charging carried by a magnetic force.

According to the present invention, there is provided a charging apparatus comprising the above-mentioned magnetic particles for charging carried by magnetic force on an image carrier on which an electrostatic latent image is formed and a magnet having a conductor to which a voltage is applied. A charging device that charges the image carrier by bringing a member into contact with the image carrier, an exposure device that forms an electrostatic latent image by exposing the surface of the image carrier charged by the charging device, An image forming apparatus comprising: a developing device that visualizes an electrostatic latent image formed on the surface of an image carrier with toner; and a transfer device that transfers a toner image visualized by the toner to a transfer material. .

Further, the present invention is used in an image forming apparatus for forming an image by visualizing an electrostatic latent image formed on an image carrier with toner and transferring the visualized image to a transfer material. A charging member comprising a magnetic body having a conductor to which a voltage is applied, and the charging magnetic particles supported by a magnetic force; an image carrier on which an electrostatic latent image is formed; At least one selected from the group consisting of a developing device for visualizing the electrostatic latent image formed on the surface of the carrier with toner, and a cleaning device for removing toner remaining on the image carrier after being visualized by the toner; A process cartridge which integrally supports the image forming apparatus and is detachable from the image forming apparatus main body.

[0018]

Embodiments of the present invention will be described below in detail.

<Charging Magnetic Particles> By using the charging magnetic particles having the above-described structure, remarkable effects were obtained on the durability of the charging magnetic particles and the image quality of the formed image. The cause of the deterioration of the durability of the magnetic particles for charging is that the surface of the magnetic particles for charging is contaminated by foreign substances such as toner or toner components and paper powder mixed into the charging member carrying the magnetic particles for charging. , The surface of the image bearing member (photoreceptor) cannot be sufficiently charged. Further, it has been found that if the contact between the magnetic particles for charging and the surface of the image carrier is insufficient, local charging unevenness occurs, and thus, it appears as subtle color unevenness particularly in a full-color image. Further, in an environment with low humidity, the image carrier cannot be sufficiently charged for a long period of time, that is, it is difficult to obtain sufficient durability, and it is easy to cause unevenness of a full-color image.

The effects on the image caused by the above problems are as follows. That is, taking an image in the case of using the reversal development method as an example, when an endurance test of continuous copying is advanced, an ghost image is generated at an image carrier period even if the image has no problem at the beginning. The charge potential of the image carrier at the time when this ghost image is generated is equal to that at the beginning.
Further endurance testing will cause fog. At this time, the charged potential of the photoconductor has deteriorated from the initial state, and a sufficient potential for obtaining an image without fogging cannot be obtained.

The ghost is caused by a difference in electric potential between an exposed portion and an unexposed portion on the image carrier. That is, the charging uniformity when charging a portion having a low absolute value of the potential (exposed portion) is inferior to the charging uniformity when charging a portion having a high absolute value of the potential (unexposed portion). . Therefore, the history of the potential of the image carrier appears as a ghost image.

As a mechanism that causes such an image problem, the following can be considered for a ghost image. (A) The difference in the charged potential between the exposed portion and the non-exposed portion of the image carrier is large. (B) A toner component that cannot be completely cleaned remains on the exposed portion of the image carrier, which hinders the contact between the magnetic particles for charging and the surface of the image carrier, causing unevenness in the charging potential.

When the exposed portion and the non-exposed portion are charged, if the two charged potentials are different, the history of the previous image formation remains and a ghost image occurs. The ghost image is generated not only by the charging method using magnetic particles but also by a corona charging method or a roller charging method.

However, in the case of the charging method using magnetic particles, even if the charged potentials of the exposed portion and the non-exposed portion are equal, slight unevenness of the potential is reflected, and a ghost image is easily generated. This can be said to be a problem peculiar to the charging method using particles.

The above-mentioned problems are caused by the fact that the correlation between the potential of the image carrier and the image quality cannot be obtained as long as the charging potential of the image carrier is measured by the conventional method. It turns out that it is a specific problem. Further, these are characteristics that are not required at all for magnetic particles for a development carrier.

Further, in the case of a so-called cleanerless image forming apparatus having no independent cleaning device, in particular, since the portion where the transfer residual toner exists and the exposed portion of the image carrier coincide with each other, a ghost image of the ghost image is formed. In order to prevent the occurrence, the conditions become particularly severe. Therefore, the effects of the present invention will be described by taking a cleanerless image forming apparatus as an example. The use of the charging magnetic particles of the present invention improves the contact between the charging magnetic particles and the surface of the image carrier. Therefore, the image carrier can be sufficiently charged even if there is a toner component remaining after transfer. (2) Since there is an effect of cleaning the surfaces of the magnetic particles for charging and the accumulation of foreign substances on the surface of the magnetic particles for charging is suppressed, the above-mentioned good contact property is hardly deteriorated even after long-term use. The operation and effect are obtained. As a result, a stable image can be formed over a long period of time even in a low humidity environment even when a large amount of a component that inhibits contact exists on the photoreceptor. Since a large amount of toner exists between the magnetic particles of the magnetic particles for the development carrier, a surface cleaning effect due to contact between the magnetic particles cannot be expected. As described above, the environment surrounding magnetic particles and the required characteristics are completely different between charging and developing.

As described above, among the magnetic particles constituting the magnetic particles for charging of the present invention, the magnetic particles having a maximum chord length of 5 μm or more have a ratio of the minor axis length to the major axis length (minor axis length). (Length / major axis length) is 0.08 or more. If this standard deviation is smaller than the above range, the variation in the shape of the magnetic particles is too small, and the mutual effect of cleaning the surfaces is not sufficient. This is because there is a shape suitable for cleaning with respect to the load between charged particles, and a variation in the shape of the magnetic particles causes a sharp edge of one magnetic particle to scrape off contamination of another magnetic particle, thereby cleaning the surface. It is considered to have an effect.

The maximum chord length of the magnetic particles is 5 to 5.
The standard deviation of the minor axis length / major axis length of the 20 μm portion is 0.
A value of 08 or more is preferable because the surface cleaning effect is further improved. It is more preferable that this standard deviation is 0.10 or more.

The maximum chord length of a magnetic particle refers to the maximum value of the length between any two points on the surface of the magnetic particle. In the present invention, the lengths of the short axis and the long axis of the magnetic particles are the lengths of the short axis and the long axis of the ellipse when the process of replacing the shape of the two-dimensional image of the magnetic particles such as an electron microscope image with the ellipse is performed. Can be.

The following is an example of a method of measuring the standard deviation of the length of the short axis / the length of the long axis. Hitachi FE-SEM (S-8
00), 100 magnetic particle images magnified 500 times are extracted at random, and based on the image information, for example, I
Statistical processing of the result of the image analysis is performed by the image analyzer V10 (manufactured by Toyobo Co., Ltd.). The details of the analysis are as follows. First, from an electron micrograph, an image signal that has passed through a stereomicroscope is input to an analyzer, and the image information is binarized. Next, the following analysis is performed based on the binarized image information. For more information, see Image Analysis
r V10 (manufactured by Toyobo Co., Ltd.) has a detailed description, but if the method is briefly described, the shape of the object is replaced with an ellipse, and the length of the major axis and the minor axis of the ellipse is calculated. Find the ratio. The processing is performed as follows.

When the specific gravity of the small area Δs = Δu · Δv at the coordinates (u, v) is set to 1 with respect to the binarized shape of the magnetic particle, the particle is located at the origin (X, Y). 2
The second moment about the horizontal axis and the vertical axis (the second moment Mx about the horizontal axis and the second moment My about the vertical axis) passing through the center of gravity of the quantified shape are expressed by the following equations.

[0032]

## EQU1 ## Mx = ΣΣ (u−X) ² My = ΣΣ (v−Y) ² Synergistic moment of inertia Mxy is expressed by the following equation.

[0033]

Mxy = ΣΣ (u−X) · (v−Y) The angle θ that satisfies the following equation has two solutions.

[0034]

(Equation 3) Furthermore, the moment of inertia M in the axial direction forming an angle θ with the horizontal axis
θ is expressed by the following equation.

[0035]

## EQU4 ## Mθ = Mx · (cos θ) ² + My · (sin
θ) ² −Mxy · sin2θ By substituting the above two solutions of θ, the smaller one of the calculated Mθ becomes the main axis. Furthermore, on any axis (1 / Mθ)
^When points corresponding to ^0.5 are plotted, they form ellipses. If the principal axis coincides with the principal axis of inertia, the direction of taking a small value of Mθ is A, and the larger one is B, the following ellipse is obtained.

[0036]

A x ² + B y ² = 1 The length of the minor axis / the length of the major axis in the present invention is expressed by the following equation with respect to the above ellipse.

[0037]

(6) Short axis length / long axis length = (A / B) ^0.5 Magnetic particles having a maximum chord length of 5 μm or more, and 5
The analysis of the standard deviation of the minor axis length / major axis length of the magnetic particles having a length of from 20 μm to 20 μm indicates that the maximum chord length of the magnetic particles is 5 μm or more and 5 μm to 20 μm in the electron micrograph.
m.

The average particle size and distribution of the magnetic particles for charging were measured using a laser diffraction type particle size distribution analyzer HELOS (manufactured by JEOL Ltd.) and the particle size was measured in the range of 0.5 to 350 μm.
The range of m was measured by dividing 32 logarithms, and the average particle diameter was defined as a 50% volume median diameter.

The average particle size of the magnetic particles for charging is 10 to
Preferably it is in the range of 200 μm, 15-30 μm
More preferably, it is in the range of m. If the average particle diameter of the magnetic particles for charging is smaller than the above range, the magnetic particles for charging easily leak from the charging member, and when the magnetic particles for charging are magnetic brushes, the transportability of the magnetic particles for charging is inferior. . If the average particle size is larger than the above range, when the charging magnetic particles of the present invention are used in the injection charging method described later, the uniformity of charging of the image carrier tends to deteriorate.

Ferrite particles are preferably used as the magnetic particles used in the charging magnetic particles of the present invention.
Ferrite containing a metal element such as copper, zinc, manganese, magnesium, iron, lithium, strontium, and barium is preferably used.

As a conventional example, it is disclosed that magnetic particles obtained by kneading and grinding magnetite and a resin are used. However, since such magnetic particles contain a large amount of a resin component, there is a tendency that magnetic particles leak from a charging member much. is there. Further, in the above-mentioned resin magnetic particles, the ratio of the resin present on the surface is high, and the ratio of the magnetic particles serving as the conductive paths is low. From this fact,
Resistance tends to increase due to surface contamination by foreign matter, and it is difficult to obtain a sufficient effect of improving durability.

However, as a result of examination using only magnetic particles having the above-mentioned preferable shape distribution as charging particles for forming a full-color image, the color image, particularly the yellow color, changed in color and the color reproducibility of yellow was observed. It has been found that this causes problems. According to the study by the present inventors, it has been found that the decrease in color reproducibility is due to the presence of black-brown ultrafine particles having a particle size of about 0.1 μm together with the toner on the yellow image. The magnetic particles having a particle diameter of about 0.1 μm have a standard deviation of the short axis length / long axis length of the magnetic particles having a maximum chord length of 5 μm or more among the above magnetic particles.
When the shape of the magnetic particles is adjusted so as to be 08 or more, ultrafine particles having a size of about 0.1 μm are generated, and compared with electrostatic force, van der Waals force, and force such as generation of magnetization by miniaturization. Firmly adheres to the surface of magnetic particles having a very large particle size, cannot be removed in the ordinary classification process, and remains on the surface. In this state, when the magnetic particles are mounted on the charger and an image is formed, the ultrafine particles are separated from the surface of the magnetic particles having a relatively large particle size due to the load on the contact portion between the magnetic brush and the image carrier, and the image is formed. The toner arrives at the developing device while being attached to the surface of the carrier, and is collected by the developing device and adheres to the toner surface. When the toner to which the ultrafine particles are adhered is transferred to the image by being developed, the black-brown fine particles of about 0.1 μm are finally present in the toner fixed to the transfer material, and the color appears dull. Was confirmed.

After diligent studies, the present inventors have developed a method for improving the reduction in color reproducibility without deteriorating the characteristics as magnetic particles. That is, the magnetic particles for charging of the present invention are:
The magnetic particles, a first surface coating layer containing a first surface coating agent and covering the surface of the magnetic particles, and a second surface coating layer containing a second surface coating agent and covering the first surface coating layer; It is characterized by having.

By forming the first surface coating layer on the surface of the magnetic particles, the above-mentioned ultrafine particles of about 0.1 μm are adhered to the recesses of the magnetic particles on the surface of the magnetic particles having a relatively large particle size. Can be kept apart. Furthermore, the second
By forming a surface coating on the surface of the first surface coating layer, it is necessary to adhere ultrafine particles which cannot be sufficiently bonded to magnetic particles by the first surface coating layer alone and to protect the first coating layer. Thus, it became possible to suppress dullness of color.

Here, the first and second surface coating agents constituting the first and second surface coating layers have an alkyl chain having 6 or more carbon atoms (hereinafter sometimes referred to as “C6 or more”). Preferably, the compound contains. By using such a surface coating agent, when the magnetic particles for charging are used as a magnetic brush, it is possible to prevent the ultrafine particles from separating from the magnetic particles even when a load is applied to a contact portion with the photoconductor. can do. Therefore, it is possible to prevent the color of an image from becoming dull due to the attachment of the fine particles to the toner.

The alkyl chain preferably has 6 to 30 carbon atoms, more preferably 8 to 30 carbon atoms. If the number of carbon atoms in the alkyl chain is too large, the solvent tends to be insoluble in the solvent.
It is difficult to uniformly form the surface coating layer on the surface of the magnetic particles. Further, the fluidity of the magnetic particles for charging may be extremely deteriorated, and the charging properties may be non-uniform.

The total amount of the first and second surface coating agents is preferably 0.01 to 2.0% by mass, more preferably 0.05 to 1.0% by mass, based on the magnetic particles. It is more preferred that there be. When the amount of the first and second surface coating agents is too small, the adhesive force of the ultrafine particles to the magnetic particles is insufficient. When the amount is too large, the resistance of the magnetic particles for charging is too small. And the fluidity deteriorates, making it difficult to use as magnetic particles for charging.

Here, the abundance of the first and second surface coating agents was calculated from the loss on heating, and was analyzed by a thermobalance at 150 to 800 ° C. in a nitrogen atmosphere.
% Of mass loss.

In the case where the first and second surface coating layers are formed, the coating is performed once so that the abundance is 1.0 to 2.0% by mass. May be deteriorated, but if the coating is sequentially performed in a plurality of times, the fluidity is improved.

The first and second surface coating agents used in the first and second surface coating layers are organic compounds containing a metal selected from titanium, aluminum, silicon, and zirconium, or a coupling agent. It is preferably an agent. When such a surface coating agent is used, the surface coating agent reacts with the surface of the magnetic particles, so that the ultrafine particles can be further reduced from falling off the magnetic particles. Therefore, a stable image can be formed over a long period of time.

In the present invention, the coupling agent refers to a compound having a hydrolyzable group and a hydrophobic group in the same molecule and bonded to a central element such as silicon, aluminum, titanium and zirconium. Preferred coupling agents include silane-based coupling agents, titanate-based coupling agents, and aluminum-based coupling agents.

Examples of the silane coupling agent include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allylphenyldichlorosilane, benzyldimethyl Chlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-
Chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilyl acrylate, vinyldimethylacetoxysilane, dimethyldiethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 1,
3-divinyltetramethyldisiloxane, 1,3-diphenyltetramethyldisiloxane and the like. In addition, aminopropyltrimethoxysilane having a nitrogen atom, aminopropyltriethoxysilane, dimethylaminopropyltrimethoxysilane, diethylaminopropyltrimethoxysilane, dipropylaminopropyltrimethoxysilane, dibutylaminopropyltrimethoxysilane,
Monobutylaminopropyltrimethoxysilane, dioctylaminopropyldimethoxysilane, dibutylaminopropyldimethoxysilane, dibutylaminopropylmonomethoxysilane, dimethylaminophenyltriethoxysilane, trimethoxysilyl-γ-propylphenylamine, trimethoxysilyl-γ- Propylbenzylamine and the like.

Examples of titanate-based coupling agents include, for example, isopropoxytitanium tristearate, isopropyl tri (dioctyl phosphate) titanate, diisopropyl di (dioctyl phosphate) titanate, diisopropyl didodecylbenzenesulfonyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, Isopropyl tri (N-aminoethyl-aminoethyl) titanate, isopropyl trioctanoyl titanate, isopropyl dimethacryl isostearyl titanate, isopropyl triisostearoyl titanate, diisopropyl diisostearoyl titanate, isopropyl isostearoyl diacryl titanate, isopropyl tricumyl phenyl titanate And so on.

As the aluminum-based coupling agent,
For example, acetoalkoxy aluminum diisopropylate can be mentioned.

As the first and second surface coating agents,
It is most preferable that the compound be a compound in which a hydrolyzable group and a hydrophobic group having a structure in which six or more carbon atoms are linearly bonded to a central element selected from titanium, aluminum, silicon, and zirconium. . Further, the compound is preferably a coupling agent.

Examples of the hydrolyzable group include methoxy, ethoxy, propoxy,
An alkoxy group such as a butoxy group is used. In addition, an acryloxy group, a methacryloxy group, a modified form thereof, a halogen atom, and the like are also used.

As the hydrophobic group, those having a structure in which 6 or more carbon atoms are linearly connected are preferable. In the form of bonding with the central element, carboxylic acid esters, alkoxy, sulfonic acid esters, and phosphoric acid esters are preferable. And may be directly bonded. Further, the structure of the hydrophobic group may include a functional group such as an ether bond, an epoxy group, or an amino group.

A central element selected from titanium, aluminum, silicon and zirconium, which can be preferably used in the present invention, is bonded to a hydrolyzable group and a hydrophobic group having a structure in which six or more carbon atoms are linearly linked. Some preferred specific examples of the compound thus obtained are shown below.

[0059]

Embedded image (CH ₃ O) ₃ —Si—C ₁₂ H ₂₅ (CH ₃ O) ₃ —Si—C ₁₈ H ₃₇ (CH ₃ O) ₃ —Si—C ₈ H ₁₇ (CH ₃ O) ₂ — Si- (C ₁₂ H _{25) 2}

[0060]

Embedded image In the present invention, when the first and second surface coating layers are formed by the above coupling agents, it is preferable that each of the surface coating layers is formed only by the coupling agent. It is also possible. In this case, the amount of the resin component is preferably equal to or less than the amount of the coupling agent.

Further, the first surface coating agent constituting the first surface coating layer and the second surface coating agent constituting the second surface coating layer are different even if the above compounds are the same. You may. However, for the reasons described below,
The first surface coating agent is used for forming the second surface coating layer.
It is preferably insoluble in a solvent that dissolves or disperses the surface coating agent.

The charging magnetic particles of the present invention preferably have a volume resistance of 10 ⁴ to 10 ⁹ Ωcm.
If the volume resistivity is smaller than the above range, pinhole leak is likely to occur, and if it is larger than the above range, the charging of the photoconductor becomes insufficient. Further, from the viewpoint of preventing leakage of the magnetic particles, it is more preferable that the resistance value of the magnetic particles for charging is 10 ⁶ to 10 ⁹ Ωcm. The volume resistance can be adjusted according to the type of magnetic particles used, the types and amounts of the first and second surface coating agents used.

FIG. 1 shows an example of a sectional view of an apparatus for measuring the volume resistance of magnetic particles. First, the cell A is filled with the charging magnetic particles 17 to be measured. The electrode 1 whose periphery is insulated by an insulator 18 so as to be in contact with the charging magnetic particles 17
1 and 12 are arranged along the guide ring 13. A voltage is applied between these electrodes 11 and 12 by a constant voltage power supply 16, and a current flowing between the electrodes at that time is measured by an ammeter 14. The voltage is monitored by the voltmeter 15.
A volume resistance value is calculated from the obtained voltage and current. The measurement conditions were as follows: in an environment of a temperature of 23 ° C. and a humidity of 65%, the contact area between the charged magnetic particles for charging and the electrode was 2 cm ² , the thickness (d) of the charging magnetic particles was 1 mm, and the weight applied to the upper electrode And the applied voltage is 100 V.

Next, a preferred method for producing the charging magnetic particles of the present invention will be described.

The production method of the present invention for producing the magnetic particles for charging includes a step of pulverizing the magnetic particles and a step of coating the surface of the pulverized magnetic particles with the first surface coating agent. Forming a second surface coating layer by coating the surface of the formed first surface coating layer with a second surface coating agent.

In the method for producing the charging magnetic particles of the present invention,
The charging magnetic particles having the preferred maximum chord length as described above, the preferred short axis length / the major axis length standard deviation, and the preferred average particle size by the magnetic particle pulverizing step. Can be manufactured. When ferrite is used for the magnetic particles, a preferable method for producing ferrite particles is a method of pulverizing ferrite particles having an average particle size of 20 to 200 μm. After pulverization while controlling the shape distribution, classification may be appropriately performed. Further, a production method by pulverizing a mass of ferrite is also possible, but it is preferable to pulverize ferrite particles from the viewpoint of production efficiency.

In the step of forming the first surface coating layer, the magnetic particles and the first surface coating agent are mixed and stirred to perform surface coating. At this time, the ultrafine particles present on the surface of the magnetic particles are swept to the recessed portion by the stirring shear, and are fixed by the first surface coating agent. However, ultrafine particles that are not sufficiently immobilized by the first surface coating layer alone remain.

In the step of forming the second surface coating layer, the same treatment as in the step of forming the first surface coating layer is performed on the second surface coating agent. Thereby, the remaining ultrafine particles are further fixed and the first coating layer is protected. Thus, the charging magnetic particles of the present invention can be obtained.

As a method for forming each of the surface coating layers, both a dry method and a wet method are used. From the viewpoint of uniformity of the surface treatment, a wet method is preferably used. Examples of specific devices used in the production include a Henschel mixer, a fixed tank type stirring device having a stirring device such as a Nauter mixer and a stirring device, and a fluidized bed drying device. it can. Further, in the present invention, it is preferable to use a fixed-bed-type stirring device capable of applying a preferable shearing force for effective adhesion of the ultrafine particles.

In this specification, the surface covering layers formed on the surface of the magnetic particles are described as the first surface covering layer and the second surface covering layer, but the first and second meanings are as follows. Is
It shows the order of the surface coating, and shows that the second surface coating is performed after the first surface coating layer is formed, and separately before the first, between the first and second, and after the third. It does not exclude that a coating takes place.

By using a compound having an alkyl group of C6 or more exhibiting lubricity as described above as the first and second surface coating agents, it is possible to reduce the influence of the stirring shear on the surface of the magnetic particles during the surface treatment. In addition, the ultrafine particles immobilized on the surface of the magnetic particles are less likely to drop again by stirring. For the above reasons, it is preferable to use a coating agent having a C6 or more alkyl group having lubricity. The effect is particularly remarkable when the above compound is used as the first surface coating agent. Even when the above compound is used as the second surface coating agent, the lubricating effect can be obtained, so that magnetic particles for charging that can obtain a clear color image can be produced. Further, as the first and second surface coating agents, the above-mentioned coupling agents can also be suitably used.

In order to obtain a more uniform surface coating, it is preferable to obtain the magnetic particles for charging by dispersing or dissolving each of the above surface coating agents in a solvent and removing the solvent. When coating, the second surface coating is preferably dispersed or dissolved in a solvent in which the first surface coating does not dissolve. When a solvent in which the first surface coating agent is soluble is used when coating the second surface coating agent, the solvent attacks the first surface coating agent, which has already fixed the ultrafine particles, and removes the ultrafine particles. This is because the separation is increased.

The surface structure of the magnetic particles for charging produced by the production method of the present invention can be confirmed by the following method.

That is, the layer configuration near the surface of the magnetic particles for charging can be observed with a cross-sectional transmission microscope.
When the first and second surface coating agents contain different elements, the distribution state of the elements is observed in a layer by observing characteristic X-rays generated near the surface of the magnetic particles for charging. The magnetic particles for charging of the present invention are sequentially dissolved from the surface with a solvent having high solubility such as chloroform, and the obtained solution is subjected to infrared absorption spectrum, H or ¹³ C-NM.
By analyzing with R or the like, it can be confirmed that the constituent components of the surface layer have a gradient. Furthermore, T
OF-SIMS (time-of-flight secondary ion mass spectrometer) and ESCA (electron spectroscopy) surface analysis means can also be used.

<Charging Member, Image Forming Apparatus and Process Cartridge> Next, a charging member, an image forming apparatus and a process cartridge using the magnetic particles for charging of the present invention will be described.

FIG. 2 is a schematic view showing an example of the image forming apparatus of the present invention. The image forming apparatus according to the present invention includes the image carrier 2
A magnetic brush charging device 202 for charging the image carrier 205 by applying a voltage while being in contact with the image carrier 205; an exposure device 206 for forming an electrostatic latent image on the image carrier 205; A developing device 208 disposed near or in contact with the image carrier 205 to develop the electrostatic latent image to form a toner image and to collect transfer residual toner remaining on the image carrier 205; A transfer device 216 for transferring the toner image to the transfer material 213 and an image fixing device 201 for fixing the toner image transferred to the transfer material 213 to the transfer material 213 are provided.

The charging device 202 is a conductive sleeve 204 containing a magnet as a holding member (corresponding to a magnet body).
And the magnetic particles for charging 203 of the present invention carried on the conductive sleeve 204 by magnetic force as a charging member.

In the charging device 202 of the image forming apparatus of the present invention, the injection charging method can be preferably used. When using the injection charging method, the image carrier 205 may have a configuration including a cylindrical conductive substrate, a photosensitive layer covering the surface thereof, and a charge injection layer formed on the surface of the photosensitive layer. preferable. With such a configuration, with respect to the applied voltage,
A charged potential of 80% or more, and more preferably 90% or more can be obtained. Therefore, it is possible to realize a further ozoneless charging method as compared with the charging method interpreted by Paschen's law. In this case, when the image carrier 205 has this charge injection layer at a position farthest from the conductive substrate, D
By C charging, a potential of 90% or more of the applied voltage can be formed on the image carrier.

In order for the charge injection layer to have sufficient chargeability and satisfy the conditions that do not cause image deletion, the volume resistivity is in the range of 1 × 10 ⁸ to 1 × 10 ¹⁵ Ωcm. Is preferred. The volume resistance value is preferably 1 × 10 ¹⁰ to 1 × 10 ¹⁵ Ωcm from the viewpoint of preventing image deletion, and 1 × 10 ¹² to 1 × 10 ¹² Ωcm in consideration of environmental fluctuations.
More preferably, it is 1 × 10 ¹⁵ Ωcm. If the volume resistance value of the charge injection layer is too small, the electrostatic latent image cannot be maintained, and image deletion may occur particularly in a high-temperature and high-humidity environment. On the other hand, if the volume resistance value is too large, the image carrier 205 will be
Cannot sufficiently receive the charge from the battery, and the charging tends to be poor.

Further, in the charging device and the image forming apparatus of the present invention, the voltage applied to the charging device 202 is as follows:
Preferably, an oscillating voltage is applied. By applying the oscillating voltage, stable charging can be performed with respect to disturbance such as mechanical accuracy. In the injection charging method, when an oscillating voltage is applied, the above advantages can be obtained. However, the applied oscillating voltage is limited,
The frequency is preferably about 0 Hz to 10 kHz, and the peak-to-peak voltage is preferably 1000 V or less. In the injection charging method, the image carrier 20
This is because if the peak-to-peak voltage is too large, the potential of the image carrier 205 will undulate, and fog or reversal fog may occur. The effective peak-to-peak voltage of the oscillating voltage is 100 V or more, preferably 300 V or more.
As the waveform, a sine wave, a rectangular wave, a sawtooth wave, or the like can be used.

The charge injection layer formed on the uppermost layer of the image carrier 205 is made of a material having a medium resistance by dispersing an appropriate amount of light-transmitting and conductive particles in an insulating binder resin. It is possible. It is also effective to form an inorganic layer having the above resistance. By providing such a functional layer surface as a charge injection layer, the charging device 202 is provided.
Plays a role to hold more injected charge,
At the time of image exposure, it serves to release the electric charge to the conductive substrate to reduce the residual potential.

Here, the volume resistance value of the charge injection layer is determined by using polyethylene terephthalate (P) having a conductive film deposited on the surface.
ET), and a charge injection layer is formed on the charge injection layer.
100V in an environment of 23 ° C and 65% humidity at TER)
The voltage was applied for measurement.

The particle size of the conductive particles dispersed in the binder resin is preferably 0.3 μm or less, and most preferably 0.1 μm or less from the viewpoint of light transmission. The preferred amount of dispersion is 2 to 250 parts by mass, more preferably 2 to 190 parts by mass, per 100 parts by mass of the binder resin. If the dispersion amount of the conductive particles is less than the above range, it is difficult to obtain a preferable volume resistance value. If the dispersion amount is more than the above range, the film strength tends to decrease and the charge injection layer tends to be easily scraped. The thickness of the charge injection layer is preferably 0.1 to 1
0 μm, optimally 1 to 7 μm.

Preferably, the charge injection layer contains a lubricant powder. Expected effects include a reduction in friction between the image carrier 205 and the charging device 202 during charging, an increase in a nip involved in charging, and an improvement in charging characteristics. Further, since the releasability of the surface of the image carrier 205 is improved, the magnetic particles for charging are less likely to adhere. As the lubricant particles, it is particularly preferable to use a fluororesin, a silicone resin, or a polyolefin resin having a low critical surface tension. Particularly preferred is a tetrafluoroethylene resin. In this case, the addition amount of the lubricant powder is preferably 2 to 50 parts by mass, more preferably 5 to 40 parts by mass with respect to 100 parts by mass of the binder resin. If the amount of the lubricant powder is less than the above range, the amount of the lubricant powder is not sufficient, so that the effect of improving the chargeability of the image carrier 205 is not sufficient. It tends to increase. If the amount is too large, the resolution of the image and the sensitivity of the photosensitive layer tend to decrease.

When the inorganic layer is coated on the surface layer as the charge injection layer, the photosensitive layer below the inorganic layer is preferably amorphous silicon, and a blocking layer and a blocking layer are formed on the conductive substrate by glow discharge or the like. It is preferable to sequentially form a photosensitive layer and a charge injection layer.

As the photosensitive layer, conventionally known ones can be used. For example, if it is an organic material, a phthalocyanine pigment, an azo pigment or the like can be used. Further, an intermediate layer may be provided between the photosensitive layer and a surface protective layer such as a charge injection 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 the conductive substrate of the image carrier 205, aluminum, nickel, stainless steel, steel, or the like, or a metal or a plastic having a conductive film, glass, or conductive paper can be used.

As described above, in the image forming apparatus of the present invention, when the voltage applied to the image carrier is a DC voltage on which an oscillating voltage is superimposed, the vibration sound caused by the oscillating electric field is reduced. This is presumably because vibrations are absorbed due to variations in the shape of the magnetic particles for charging. Furthermore,
When the thickness of the conductive base of the image carrier is 0.5 to 3.0 mm, the effect is further enhanced. If the thickness of the conductive substrate is smaller than the above range, the dimensional stability is poor, and if the thickness is larger than the above range, the rotational torque is increased or the material cost is increased. Absent.

There is also a preferable range in the triboelectric charging property between the used toner and the magnetic particles 203 for charging of the charging device 202. The tribo value of the toner to be measured may be the same as the charging polarity of the image carrier 205, and its absolute value may be 1 to 90 mC / Kg, preferably 5 to 80 mC / Kg, more preferably 10 to 40 mC.
/ Kg. If the absolute value of the tribo value is within the above range, the toner is taken in, swept out, and the image carrier 20 is discharged.
5 is good for the charging characteristics.

A preferred method for measuring the above values is as follows. First, in an environment of a temperature of 23 ° C. and a relative humidity of 60%, a toner 200 m
g of the mixture is placed in a polyethylene bottle of 50-100 ml capacity and shaken by hand 150 times. The mixture of the toner and the magnetic particles for charging is charged into the charging device 202 as magnetic particles for charging. Next, the image carrier 205 to be used
Is mounted on the image forming apparatus, and a DC bias having the same polarity as the charging polarity of the toner is applied to the charged portion, and the metal drum is driven under the conditions for charging the image carrier. At this time, the charge amount of the toner transferred from the charging device 202 onto the metal drum is measured.

In the image forming apparatus of the present invention, when a magnetic brush is used as a charging member that comes into contact with the image carrier 205, the configuration is such that a magnet roll is used as a member (magnet) for holding magnetic particles for charging. Or, the surface of a conductive sleeve with a magnet roll inside, the one coated uniformly with magnetic particles for charging is used,
In particular, a conductive sleeve having a magnet roll and the surface of which is uniformly coated with magnetic particles for charging is preferably used.

The closest gap between the member for holding the charging magnetic particles (the conductive sleeve 204 which is a conductor of the magnet body) and the image carrier 205 is preferably 0.3 to 2.0 mm. If the gap is smaller than the above range, a leak may occur between the conductive portion of the holding member of the magnetic particles for charging and the image carrier 205 depending on the applied voltage, and the image carrier 205 may be damaged. is there.

The charging magnetic brush does not move in the forward or reverse direction at the contact portion with respect to the moving direction of the image carrier 205, but from the viewpoint of taking in the transfer residual toner, the charging magnetic brush moves in the opposite direction. It is preferable to move.

The amount of the charging magnetic particles 203 held by the charging magnetic particle holding member 204 is preferably 50 to 5
00 mg / cm ² , more preferably 100 to 300 mg
/ Cm ² , a stable chargeability can be obtained.

Further, as shown in the figure, an extra charging magnetic particle 203 may be held in the charging device 202 and circulated.

As the image exposure apparatus, known means such as a laser and an LED can be used.

In the present image forming apparatus, a preferable step in the cleanerless image forming method can be added. After the transfer step in the image forming apparatus of the present invention,
In addition, by providing the potential control member for the image carrier before the charging step, the stability of the image forming apparatus is further improved.

As the potential control member, a member that emits light to control the potential on the surface of the photoreceptor, a conductive roller, a blade, a fur brush, or the like that is disposed in contact with or in close proximity thereto is used. Among these, rollers and fur brushes are particularly preferably used. In the case where a voltage is applied to these control agents to control the potential of the image carrier, it is preferable that the polarity is controlled to be opposite to that of the image carrier charging step. The reason is,
This is because, before the image carrier charging step, the potential of this image carrier is adjusted to a lower side, and the history of the previous formed image is erased to help uniform charging.

The developing means used in the developing device 208 is not particularly limited, but in the case of an image forming apparatus having no independent cleaning means, reversal development is preferable.
As shown in FIG. 2, a configuration in which the developer 211 and the image carrier 205 are in contact with each other is preferable. For example, a contact two-component development method, a contact one-component method, and the like can be mentioned as suitable development methods. This is because, when the developer 211 and the transfer residual toner are in contact with each other on the image carrier 205, an electrostatic sliding force is applied, and the transfer residual toner can be effectively collected in the developing device 208. It is preferable that the DC component of the bias applied to the developing device 208 be between the black portion (image exposed portion) and the potential of the white background portion. Note that reference numeral 207 denotes a developer carrying member, and 209 and 210 denote stirring screws.

Further, as a transfer unit used in the transfer device 216, a known method such as a corona, a roller, and a belt is used. FIG. 2 shows a transfer device 216 using the transfer roller 214. In addition, 212 is a paper conveyance guide, and 215 is a paper conveyance belt.

Further, the transfer residual toner is collected from the collected charging device 202 through the surface of the image carrier 205 to the developing device 2.
When the sheet is transported to the image carrier 08 and collected and reused, the image carrier 20
This can be realized without changing the charging bias of No. 5, but practically, when the transfer paper jams or when images with a high image ratio are continuously formed, the toner is mixed into an excessive amount of the toner charger. The case is conceivable. In this case, during the image forming operation, it is possible to move the toner from the charging device to the developing device using the time during which no image is formed on the image carrier 205. The non-image forming time includes the time of pre-rotation, the time of post-rotation, and the interval between transfer sheets. In this case, it is also preferable to change the charging bias so that the toner easily moves to the image carrier 205 from the charging device 202.
As the bias at which the toner is easily transferred from the charging device 202, the peak-to-peak voltage of the AC component is set to a small value or the DC component. Alternatively, there is a method of lowering the AC effective value by changing the waveform while keeping the peak-to-peak voltage the same.

Further, according to the present invention, the life of the charging device 202 and the non-magnetic sleeve
In consideration of the use of the toner, it is preferable to adopt a configuration in which toner can be further added according to cost requirements. In such a case, it is preferable that the magnetic particles for charging are present in the charged portion in a larger amount than the minimum required amount, and the durability is further increased by circulating the magnetic particles.

As means for circulating, it is preferable to mechanically stir, or to provide a magnetic pole structure capable of circulating magnetic particles, or to provide a member for moving magnetic particles in a container for storing magnetic particles. preferable. For example, a screw member for stirring, a structure in which a repulsion pole is provided and recoating is performed while peeling off magnetic particles, and an obstruction member for preventing flow of magnetic particles are provided behind the magnetic brush.

In the present invention, the image bearing member, the charging member,
Further, a process cartridge (217 in FIG. 2) detachably mountable to the main body of the image forming apparatus can be provided by integrally supporting the developing means and the cleaning means as required. Further, the developing means can be a cartridge separate from the cartridge having the image carrier (218 in FIG. 2).

Examples of the full-color image forming apparatus in which the magnetic particles of the present invention are preferably used include the following embodiments.

First, there is a device having a plurality of units each having one developing device arranged on one image carrier. An example is shown in FIG. In FIG. 3, the transfer bias applying means 30
a, image carrier (photoreceptor) 31a, charging device (primary charger) 32a using magnetic particles for charging of the present invention, developing device 3
A unit including a transfer blade 3a, a transfer blade 34a, a toner hopper 35a, a supply roller 36a, and an exposure device 37a is arranged for each color toner for forming a color image. In the drawing, Pa, Pb, Pc, and Pd indicate units that form images using yellow, magenta, cyan, and black color toners, respectively. Reference numeral 301 denotes a belt driven roller; 302, a belt removing machine; 303, a registration roller;
05 is a transfer material carrying / conveying member, 306 is a transfer belt cleaning device, 307 is a driving roller, 308 is a separation charger, 309 is a fixing device, 310 is a web, 311 is a temperature detecting unit, 312 and 313 are heating units, and 314 is The fixing roller 315 is a pressure roller, which is generally used in a conventional image forming apparatus. In the figure, a
And e represent the direction of rotation.

A structure in which a plurality of developing devices according to the type of the color toner to be used are sequentially arranged on one image carrier, or a development by a plurality of developing devices is performed on the image carrier. One having a movable configuration capable of sequentially performing processing is exemplified. Examples are shown in FIGS.

In FIG. 4, reference numeral 401 denotes exposure light, and 402 denotes a charging device (primary charging device) using the magnetic particles for charging of the present invention. Reference numerals 403 denote developing devices 403a to 403 for developing with color toners such as yellow, cyan, magenta, and black for forming a full-color image.
d is a developing device unit. Further, 404 is a fixing device, 405 is a photoreceptor, 406 is a photoreceptor cleaning device, 407 is a transfer member, 408 is a transfer material conveying means, 409 is a transfer means, 410 is a registration roller, 411 is a pickup roller, 412 is a transfer roller. It is a material cassette.

In FIG. 5, reference numeral 501 denotes a developing device 501a for developing with a color toner of yellow, cyan, magenta, black or the like for forming a full-color image.
To 501d. Reference numerals 401 to 412 are the same as those in FIG.

In the present invention, as the toner used in the developing device, any of toner particles produced by a pulverization method or a polymerization method can be used, but a toner produced by a polymerization method, particularly a suspension polymerization method, can be used. Particles are preferably used. Also, a seed polymerization method in which a monomer is further adsorbed to the polymer particles once obtained and then polymerized using a polymerization initiator can be suitably used in the present invention.

In the production of toner particles by a pulverization method, components such as a binder resin, a colorant, and a charge control agent are sufficiently mixed by a ball mill or other mixer, and then mixed with a heat kneader such as a hot roll kneader or an extruder. After kneading well, solidifying by cooling, and then mechanically pulverized and classified to obtain toner particles. Further, after classification, toner particles subjected to a hot air treatment or a spheroidization treatment by applying a mechanical impact are more preferable.

Examples of the type of the binder resin used in the production of the toner particles by the pulverization method include, for example, styrene such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene and a homopolymer of a substituted product thereof; styrene-p
-Chlorostyrene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-chloromethyl methacrylate copolymer Polymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer Styrene-based copolymers such as styrene-acrylonitrile-indene copolymer; polyvinyl chloride, phenolic resin, natural modified phenolic resin, natural resin modified maleic acid resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin, polyester Fat, polyurethane, polyamide resins, furan resins, epoxy resins, xylene resins, polyvinyl butyral, terpene resin, coumarone-indene resin, petroleum resin, or the like can be used. Further, a crosslinked styrene resin is also a preferable binder resin.

In the case where a polymerization method is used for the production of toner particles, it is possible to specifically produce the toner particles by the following production method. Monomer obtained by adding a release agent, colorant, charge control agent, polymerization initiator, and other additives consisting of a low softening point substance to a monomer, and then dissolving or dispersing it uniformly using a homogenizer, ultrasonic disperser, etc. The composition
It is dispersed in an aqueous phase containing a dispersant by a conventional stirrer, homomixer, homogenizer or the like. Preferably, the stirring speed and time are adjusted so that the droplets of the monomer composition have the desired size of the toner particles, and granulation is performed.
Thereafter, stirring may be performed by the action of the dispersant to such an extent that the particle state is maintained and the sedimentation of the particles is prevented. The polymerization is performed at a polymerization temperature of 40 ° C. or higher, generally 50 to 90 ° C. Further, the temperature may be raised in the latter half of the polymerization reaction, and in the present invention, for the purpose of improving the durability properties, in order to remove unreacted polymerizable monomers, by-products and the like, the latter half of the reaction, or the end of the reaction. Later, a part of the aqueous medium may be distilled off. After the reaction, the generated toner particles are collected by washing and filtration, and dried. In the suspension polymerization method, it is usually preferable to use 300 to 3000 parts by weight of water as a dispersion medium with respect to 100 parts by weight of the monomer system.

In the present invention, a toner having a core / shell structure in which a material having a low softening point is coated with a shell resin is preferably used. The function of the core / shell structure is that the anti-blocking property can be imparted without deteriorating the excellent fixability of the toner, and the polymerization of only the shell portion is more effective than the polymerization of a bulk toner having no core. This is because the residual monomer can be easily removed in the post-treatment step after the step.

The toner having a core / shell structure can be obtained by setting the polarity of the material in the aqueous medium to be smaller for the low softening point substance than for the main monomer. Specific examples of the low softening point substance include paraffin wax, microcrystalline wax, polyolefin wax, Fischer-Tropsch wax, carnauba wax, amide wax, alcohol, higher fatty acid, acid amide wax, ester wax, ketone, and hydrogenated castor oil. , Plant, animal, mineral, petrolactam and their derivatives or their graft / block compounds.

The low softening point substance is 5% based on toner particles.
It is preferable to add 〜30% by mass. If the addition is less than 5% by mass, it takes a burden to remove the above-mentioned residual monomers. If the addition exceeds 30% by mass, coalescence of toner particles is likely to occur during granulation even in production by a polymerization method. Those having a wide distribution were easily formed, and were not suitable for the present invention.

As the outer shell resin forming the shell portion, generally used styrene- (meth) acrylic copolymers, polyester resins, epoxy resins, and styrene-butadiene copolymers are preferable. The following monomers are preferably used as a monomer for obtaining a styrene-based copolymer. Styrene monomers such as styrene, o- (m-, p-) methylstyrene, m- (p-) ethylstyrene; methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate , Butyl (meth) acrylate, octyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, behenyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (meth) acrylic acid (Meth) acrylate monomers such as dimethylaminoethyl and diethylaminoethyl (meth) acrylate; ene monomers such as butadiene, isoprene, cyclohexene, (meth) acrylonitrile and acrylamide are preferably used. These can be used alone or generally in the published Polymer Handbook, 2nd edition III-P 139-192 (J
The monomers are appropriately mixed and used so that the theoretical glass transition temperature (Tg) described in “Own Wiley & Sons” indicates 40 to 75 ° C. Theoretical glass transition temperature is 40 ℃
If the temperature is less than 75 ° C., problems will occur in terms of the storage stability of the toner and the durability stability of the developer. On the other hand, if the temperature exceeds 75 ° C., the fixing point will increase. And the color reproducibility is poor, and the transparency of the OHP image is significantly reduced, which is not preferable from the viewpoint of high image quality. The molecular weight of the shell resin is GPC
(Gel permeation chromatography). As a specific GPC measurement method, a toner is extracted in advance with a toluene solvent using a Soxhlet extractor for 20 hours, and then toluene is distilled off with a rotary evaporator. An organic solvent that cannot be dissolved, such as chloroform, was added thereto, and the mixture was sufficiently washed. A solution obtained by filtering a solution dissolved in THF (tetrahydrofuran) through a solvent-resistant membrane filter having a pore diameter of 0.3 μm was collected by Waters Co., Ltd.
0C and the column configuration was A-801, 80 manufactured by Showa Denko
2, 803, 804, 805, 806 and 807 can be linked to measure the molecular weight distribution using a standard polystyrene resin calibration curve. The number average molecular weight (Mn) of the obtained resin component is
5000 to 1,000,000, and a weight average molecular weight (M
w) and the number average molecular weight (Mn) ratio (Mw / Mn) is 2
Resins having a value of from 100 to 100 are preferably used.

In the present invention, when a toner having a core / shell structure is produced, it is particularly preferable to add a polar resin in addition to the outer shell resin in order to incorporate a low softening point substance into the outer shell resin. . As the polar resin used in the present invention, a copolymer of styrene and (meth) acrylic acid, a maleic acid copolymer, a saturated polyester resin, and an epoxy resin are preferably used. It is particularly preferable that the polar resin does not contain an unsaturated group capable of reacting with a shell resin or a monomer in the molecule. If a polar resin having an unsaturated group is included, a cross-linking reaction occurs with the monomer forming the outer shell resin layer. It is disadvantageous and not preferred.

In the present invention, an outermost resin layer may be further provided on the surface of the toner particles.

The glass transition temperature of the outermost resin layer is designed to be equal to or higher than the glass transition temperature of the outer resin layer in order to further improve the blocking resistance, and is crosslinked so as not to impair the fixability. Is preferred. The outermost resin layer preferably contains a polar resin and a charge control agent for improving the chargeability. The method for providing the outermost shell layer is not particularly limited, and examples thereof include the following methods. (1) In the second half of or after the polymerization reaction, if necessary, a monomer in which a polar resin, a charge control agent, a cross-linking agent, etc. are dissolved and dispersed is added to the reaction system, the polymer is adsorbed on polymer particles, and a polymerization initiator is added. To conduct polymerization. (2) If necessary, add emulsion polymerization particles or soap-free polymerization particles comprising a monomer containing a polar resin, a charge control agent, a cross-linking agent, etc. to the reaction system, and agglomerate on the surface of the polymerization particles, if necessary. A method of fixing by heat or the like. (3) A method in which emulsion polymerized particles or soap-free polymerized particles comprising a monomer containing a polar resin, a charge control agent, a cross-linking agent, etc., are mechanically fixed to the toner particle surfaces in a dry manner as required.

As a specific method for encapsulating the low softening point substance, the polarity of the material in the aqueous medium is set to be lower for the low softening point substance than for the main monomer, and a small amount of a large polar resin or By adding a monomer, a toner having a core / shell structure can be obtained.

The particle size distribution and the particle size of the toner particles are controlled by changing the type and amount of the hardly water-soluble inorganic salt or the dispersant acting as a protective colloid, or by changing the mechanical device conditions such as the rotor peripheral speed and the number of passes. A toner having a desired particle size can be obtained by controlling the stirring conditions such as the shape of the stirring blade, the shape of the container, and the concentration of the solid content in the aqueous solution.

Examples of the binder resin for toner used for pressure fixing include low molecular weight polyethylene, low molecular weight polypropylene, ethylene-vinyl acetate copolymer, ethylene-acrylate copolymer, higher fatty acid and polyamide. Resins and polyester resins. These are preferably used alone or as a mixture. In particular, in the present invention, when a polymerization method is used as a method for producing toner particles, it is preferable that the method does not have polymerization inhibition and has no solubilized substance in an aqueous system.

In the present invention, in order to faithfully develop finer latent image dots for higher image quality, the yellow, magenta, cyan and black toner particles have a weight average particle diameter of 2 to 9 μm and have higher image quality. 3 to prevent fog and scattering
It is preferably about 9 μm. 2 μm weight average particle size
In toner particles having a particle size of less than 1, toner remaining on the photoreceptor due to a decrease in transfer efficiency is large, and further, it is likely to cause non-uniform unevenness of an image due to fog or poor transfer. Therefore, the toner used in the present invention is preferable. Absent. If the weight average particle size of the toner particles exceeds 9 μm, characters and line images are liable to be scattered.

In the present invention, the toner particles have a shape factor SF-1 of 100 to 140 and a shape factor SF-2 of 100.
Preferably it is ~ 120.

The charge control agents used in the present invention include:
Although a known toner can be used, in the case of a color toner, a charge control agent which is colorless, has a high toner charging speed, and can stably maintain a constant charge amount is particularly preferable. Further, in the case where a direct polymerization method is used in the present invention, a charge control agent having no polymerization inhibitory property and having no soluble substance in an aqueous system is particularly preferable. Specific examples of negative compounds include metal compounds of salicylic acid, naphthoic acid, and dicarboxylic acid, sulfonic acids, high molecular compounds having carboxylic acids as side chains, boron compounds, urea compounds, silicon compounds, calixarenes, and the like. Available, quaternary ammonium salt as positive system,
A polymer compound having the quaternary ammonium salt in a side chain,
Guanidine compounds, imidazole compounds and the like are preferably used. The charge control agents described above are preferably used in the form of fine particles. In this case, the number average particle diameter of these charge control agents is preferably 2 μm or less, more preferably 1 μm or less. The charge control agent is 0.05 to 100 parts by mass of the resin.
5 parts by weight are preferred. However, in the present invention, the addition of a charge control agent is not essential, and in the case where a two-component developing method is used, even when a non-magnetic one-component blade coating developing method is used utilizing frictional charging with a carrier. It is not always necessary to include a charge control agent in the toner by positively utilizing the triboelectric charging with the blade member and the sleeve member.

When the polymerization method is used in the present invention, for example, 2,2'-azobis- (2,4
-Dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 1,1'-azobis (cyclohexane-1-carbonitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvalero Azo-based polymerization initiators such as nitrile and azobisisobutyronitrile; and peroxide-based polymerization initiators such as benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide and lauroyl peroxide. Used. The amount of the polymerization initiator varies depending on the desired degree of polymerization, but is generally used in an amount of 0.5 to 20% by mass based on the monomer. The type of the initiator slightly varies depending on the polymerization method, but is used alone or in combination with reference to the 10-hour half-life temperature.

Further, in order to control the degree of polymerization, a known crosslinking agent, chain transfer agent, polymerization inhibitor and the like can be further added and used.

Examples of the dispersing agent include inorganic oxides such as tricalcium phosphate, magnesium phosphate, aluminum phosphate, zinc phosphate, calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, and aluminum hydroxide. Examples thereof include calcium metasilicate, calcium sulfate, barium sulfate, bentonite, silica, alumina, a magnetic substance, and ferrite. Examples of organic compounds include polyvinyl alcohol, gelatin, methyl cellulose, methyl hydroxypropyl cellulose,
Ethyl cellulose, sodium salt of carboxymethyl cellulose and starch are used by being dispersed in an aqueous phase. These dispersants are used in an amount of 0.1 to 100 parts by mass of the polymerizable monomer.
It is preferable to use 2 to 10.0 parts by mass.

As these dispersants, commercially available ones may be used as they are. However, in order to obtain finely dispersed particles having a uniform particle size, it is necessary to form the inorganic compound under high-speed stirring in a dispersion medium. Can also. For example, in the case of tricalcium phosphate, a dispersant suitable for a suspension polymerization method can be obtained by mixing an aqueous solution of sodium phosphate and an aqueous solution of calcium chloride under high-speed stirring. Further, 0.001 to 0.1 parts by mass of a surfactant may be used in combination for making these dispersants finer. Specifically, commercially available nonionic, anionic, and cationic surfactants can be used. For example, sodium dodecyl sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate,
Sodium oleate, sodium laurate, potassium stearate and calcium oleate are preferably used.

As the coloring agent used in the present invention, carbon black, a magnetic substance, and those toned to black using the following yellow / magenta / cyan coloring agents are used.

Examples of yellow colorants include condensed azo compounds, isoindolinone compounds, anthraquinone compounds,
Compounds represented by azo metal complexes, methine compounds and allylamide compounds are used. Specifically, C.I. I. Pigment Yellow 12, 13, 14, 15, 17, 6
2, 74, 83, 93, 94, 95, 97, 109, 1
10, 111, 120, 127, 128, 129, 14
7, 168, 174, 176, 180, 181, 191
Is preferably used.

As the magenta coloring agent, condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinones, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds and perylene compounds are used. Specifically, C.I.
I. Pigment Red 2, 3, 5, 6, 7, 23, 4
8; 2, 48; 3, 48; 4, 57; 1, 81; 1, 1
44, 146, 166, 169, 177, 184, 18
5, 202, 206, 220, 221, 254 are particularly preferred.

As the cyan coloring agent, copper phthalocyanine compounds and derivatives thereof, anthraquinone compounds and basic dye lake compounds can be used. Specifically, C.I. I. Pigment Blue 1, 7, 15, 15; 1, 15; 2, 1
5; 3, 15; 4, 60, 62, 66 can be particularly preferably used.

These coloring agents can be used alone or as a mixture, or in the form of a solid solution. The colorant of the present invention is selected from the viewpoints of hue angle, saturation, brightness, weather resistance, OHP transparency, and dispersibility in toner. The colorant is used in an amount of 1 to 20 parts by mass per 100 parts by mass of the resin.

The external additives of the toner usable in the present invention include oxides such as alumina, titanium oxide, silica, zirconium oxide and magnesium oxide, as well as silicon carbide, silicon nitride, boron nitride and aluminum nitride. , Magnesium carbonate, and organosilicon compounds.

Among them, as the inorganic oxide fine particles, alumina, titanium oxide, zirconium oxide, magnesium oxide or silica-treated fine particles thereof are preferable for stabilizing the charging of the toner regardless of temperature and humidity.
Further, alumina or titanium oxide fine particles or silica surface-treated fine particles thereof are preferable for improving the fluidity of the toner.

It is preferable that the inorganic oxide fine particles have been subjected to a hydrophobic treatment in order to reduce the dependence of the charge amount of the toner on the environment such as temperature and humidity and to prevent the toner from being released from the toner surface. Examples of the hydrophobizing agent include coupling agents such as silane coupling agents, titanium coupling agents, and aluminum coupling agents, and oils such as silicone oils, fluorine-based oils, and various modified oils. In particular, among the above-mentioned hydrophobizing agents, the coupling agent particularly reacts with the residual groups on the inorganic oxide fine particles or the adsorbed water to achieve a uniform treatment, thereby stabilizing the charge of the toner and imparting fluidity. preferable.

The carrier used in the present invention preferably has a volume resistivity of 10 ⁹ to 10 ¹⁵ Ωcm. More preferably, the volume resistance value is 10 ¹³ to 10 ¹⁵ Ωcm. If the volume resistivity of the carrier is smaller than the above range, the latent image may be disturbed due to injection of a developing bias in the developing region due to low resistance. On the other hand, if the volume resistance value of the carrier is larger than the above range, the carrier itself is charged up, and the ability to impart charge to the replenishment toner is likely to decrease, which is not preferable.

The carrier preferably used in the present invention is a magnetic powder-dispersed resin carrier in which a magnetic powder such as iron powder or ferrite iron oxide is dispersed in a resin, or Mn, C
It is a ferrite carrier containing u, Zn, Ni, Sr, and Mg.

Examples of the resin in which the magnetic powder is dispersed include a styrene- (meth) acrylic copolymer, a polyester resin, an epoxy resin, a styrene-butadiene copolymer, an acid resin, and a melamine resin. Further, it is preferable that the carrier is coated with a silicone resin, an acrylic resin, a fluororesin or the like to prevent toner spent.

[0142]

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

First, the structure, material, manufacturing method and the like of the members used in the present invention will be exemplified.

<Production Example 1 of Magnetic Particles> Fe ₂ O ₃ 54 mol% MnO 30 mol% MgO 16 mol% The above-mentioned oxide was pulverized and mixed by a ball mill, and a dispersant, a binder and water were added thereto to form a slurry. After that, a granulation operation was performed with a spray drier. After appropriately classifying, the mixture is fired at 1200 ° C. in an atmosphere in which the oxygen concentration is adjusted. After crushing, the shape is adjusted using a ball mill, and the maximum chord length is 5 mm.
The standard deviation of the minor axis length / major axis length of the particles of not less than μm and 5 to 20 μm is 0.12 and 0.14, respectively.
Ferrite powder having an average particle size of 19 μm and a volume resistance value of 4 × 10 ⁷ Ωcm was obtained. This was designated as Magnetic Particle 1.

<Production Example 2 of Magnetic Particles> In Production Example 1 of magnetic particles, the maximum chord length was 5 μm or more and 5 to 20 μm by the same method as in Production Example 1 except that the shape adjustment conditions were changed. The standard deviation of the minor axis length / major axis length of the particles is 0.09 and 0.11, respectively, and the average particle size is 22.
A ferrite powder having a volume resistivity of 3 × 10 ⁷ Ωcm was obtained. This was designated as magnetic particles 2.

<Comparative Production Example of Magnetic Particles> Iron oxide was pulverized with a ball mill, a dispersant, a binder, and water were added to form a slurry, and then a granulation operation was performed using a spray drier. After appropriately classifying, firing in an atmosphere in which the oxygen concentration is adjusted, crushing, and shape adjustment using a ball mill, the short axis length of particles having a maximum chord length of 5 μm or more and 5 to 20 μm / The standard deviation of the major axis length is 0.06,
And 0.07, an average particle size of 22 μm, and a volume resistance of 4
A magnetite powder of × 10 ³ Ωcm was obtained. This was designated as magnetic particles 3.

<Production Example 3 of Magnetic Particles> A minor axis length of a particle having a maximum chord length of 5 μm or more and 5 to 2 μm was obtained in the same manner as in the comparative production example of magnetic particles, except that the shape adjustment conditions were changed. Standard deviation of length / long axis length is 0.1
1, 0.13, and a magnetite powder having an average particle size of 19 μm were obtained. The magnetite powder is oxidized by heating it in oxygen, and has a volume resistivity of 4 × 10 ⁹ Ωc.
m of magnetite powder was obtained. There was no difference in the standard deviation of the minor axis length / major axis length before and after the oxidation treatment. This was designated as magnetic particles 4.

<Production Example 4 of Magnetic Particles> The magnetic particles 1 obtained in Production Example 1 of magnetic particles are subjected to an oxidation treatment by heating in air to have a volume resistance of 4 × 10 ⁸ Ωc.
m of ferrite powder was obtained. There was no difference in the standard deviation of the minor axis length / major axis length before and after the oxidation treatment. This was designated as magnetic particles 5.

<Production Example 5 of Magnetic Particles> The magnetic particles 1 obtained in Production Example 1 of magnetic particles are subjected to a reduction treatment by heating in nitrogen, and have a volume resistivity of 7 × 10 ⁶ Ωc.
m of ferrite powder was obtained. There was no difference in the standard deviation of the minor axis length / major axis length before and after the reduction treatment. This was designated as magnetic particles 6.

<Image carrier> φ30 mm, thickness 0.75 m
m, five functional layers were provided on an aluminum cylinder.
The first layer is an undercoat layer, and is a conductive layer having a thickness of about 20 μm provided to smooth defects of the aluminum drum and to prevent the occurrence of moire due to reflection of laser exposure. The second layer is a positive charge injection preventing layer, serves to prevent canceling the negative charge positive charge injected from the aluminum drum is charged photoreceptor surface, 10 by Amilan resin and methoxymethylated nylon ⁶
This is a medium resistance layer having a thickness of about 1 μm and a resistance adjusted to about Ωcm.

The third layer is a charge generation layer, which is a layer having a thickness of about 0.3 μm in which an oxytitanium phthalocyanine pigment is dispersed in a resin, and generates a positive and negative charge pair by being subjected to laser exposure.

The fourth layer is a charge transport 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. This fourth layer had a thickness of 15 μm. The surface resistance of the image carrier is
In the case of the charge transport layer alone, the value was 3 × 10 ¹⁵ Ωcm.

A charge injection layer was formed on the fifth layer. The charge injection layer is obtained by dispersing SnO ₂ ultrafine particles in a photocurable acrylic resin. Specifically, antimony-doped SnO ₂ having an average particle diameter of about 0.03 μm and having a low resistance is used.
160 parts by mass of the particles with respect to 100 parts by mass of the resin, and further,
18 parts by mass of the tetrafluoroethylene resin particles, and 1.
0 parts by mass are dispersed. The thickness of the fifth layer is 3.5 μ.
m. Thereby, the surface resistance of the image carrier is 5 ×
It became 10 ¹² Ωcm.

<Production Example of Cyan Toner> Ion-exchanged water 7
10 parts by weight was charged with 0.1M-Na ₃ PO ₄ aqueous solution 450 parts by mass, followed by heating to 60 ° C., using a TK-type homomixer (manufactured by Tokushu Kika Kogyo), and stirred at 12000 rpm. To this, 68 parts by mass of a 1.0 M CaCl ₂ aqueous solution was gradually added to obtain an aqueous medium containing a calcium phosphate salt.

Next, 165 parts by mass of styrene and 35 parts by mass of n-butyl acrylate as monomers and C.I. I. Pigment Blue 15: 3 and 14 parts by mass were finely dispersed by a ball mill, then 2 parts by mass of an aluminum salicylate compound as a charge control agent, 10 parts by mass of a saturated polyester resin as a polar resin, and ester wax (melting point of 70%) as a release agent. ° C), and add 50 parts by mass.
Using a TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.), the mixture was uniformly dissolved and dispersed at 12,000 rpm. In this, 10 parts by mass of a polymerization initiator 2,2'-azobis (2,4-dimethylvaleronitrile) was dissolved to prepare a polymerizable monomer composition.

The polymerizable monomer composition was charged into the aqueous medium, and the mixture was stirred at 10,000 rpm with a TK homomixer at 60 ° C. under an N ₂ atmosphere for 10 minutes. Granulated. Thereafter, the temperature was raised to 80 ° C. while stirring with a paddle stirring blade, and the reaction was performed for 10 hours. After completion of the polymerization reaction, the remaining monomer is distilled off under reduced pressure, and after cooling,
After adding hydrochloric acid to dissolve the calcium phosphate, the mixture was filtered, washed with water, and dried to give a weight average particle size of 6.5 μm, SF-1
Of 114 and SF-2 of 107 were obtained.

To 100 parts by mass of the obtained toner particles, 1.0 part by mass of hydrophobic titanium oxide and 1.0 part by mass of hydrophobic silica fine particles were externally added to obtain a cyan toner.

<Production Example of Yellow, Magenta, and Black Toner> A yellow toner, a magenta toner, and a black toner were obtained in the same manner as in the production example of the cyan toner except that the pigment was changed. .

<Production Example of Developing Carrier> A phenol / formaldehyde monomer (mass ratio 50: 5) was prepared in an aqueous medium.
After mixing and dispersing 0), 600 parts by mass of magnetic powder obtained by hydrophobizing magnetite particles surface-treated with alumina with isopropoxytriisostearoyl titanate and 100 parts by mass of monomer were mixed with 100 parts by mass of monomer. 400 parts by mass of the nonmagnetic hematite particles subjected to the hydrophobic treatment were uniformly dispersed, and the monomer was polymerized while appropriately adding ammonia to obtain a spherical magnetic resin carrier core material containing magnetic particles.

Further, the spherical magnetic resin carrier core material 100
The developing carrier was obtained by coating 0.5 parts by mass of an acrylic resin with respect to parts by mass. This carrier has an average particle size of 40 μm and a volume resistance value of 4 × 10 ¹³ Ωcm.

<Production Examples of Yellow, Magenta, Cyan, and Black Developers> Each of the above yellow, magenta, and cyan toners was adjusted so that the mass ratio of toner / carrier for development was 8/100.
Cyan and black toners were mixed with the above-mentioned carrier for development to prepare a developer.

<Image Forming Apparatus> A digital copying machine using a laser beam as an image forming apparatus (Canon: GP
55) was prepared. The device is generally provided with a corona charger as a charging device for an image carrier, a one-component developing device employing a one-component jumping developing method as a developing device, and a corona charger, a blade cleaning means, a pre-charging device as a transfer device. An exposure unit is provided. The charging device, the cleaning means, and the image carrier are an integrated unit. The process speed is 150 mm / s.

In this embodiment, this digital copying machine is modified as follows. First, set the process speed to 2
Modified to 00 mm / s. Next, the developed part was modified from one-component jumping development to use of a two-component developer. Further, a 16φ conductive non-magnetic sleeve containing a magnet roller is disposed on the charged portion to form a charging magnetic brush. Further, the transfer device using a corona charger was changed to a roller transfer system, and the pre-charging exposure means was removed.

The gap between the conductive sleeve of the charged portion and the image bearing member was set to 0.5 mm. The developing bias is 1000 Vpp / 3 KH to a DC component of -500 V.
A rectangular wave of z was superimposed. Further, the cleaning blade was removed to obtain a cleanerless copying machine. FIG. 2 shows a schematic diagram.

<Example 1> First, a method for producing the magnetic particles for charging 1 used in Example 1 will be described.

A fixed-tank type mixer equipped with a stirrer and a heating means was kept at 100 ° C., and 100 parts by mass of the magnetic particles 1 and 0.3 parts by mass of isopropoxytitanium tristearate as the first surface coating agent were dissolved. And the toluene solution
After heating to 180 ° C. and drying, it was allowed to cool. Next, a methanol dispersion liquid in which 0.3 parts by mass of aluminum 9-octadecenyl acetoacetate diisopropoxide was dispersed as a second surface coating agent was added, and the temperature was increased to 70 ° C. and dried to obtain the magnetic particles 1 for charging. I got The heating loss of the magnetic particles for charging 1 was 0.5% by mass. It is understood that isopropoxytitanium tristearate is soluble in toluene and has a transparent amber color, but it is brownish cloudy and insoluble in methanol.

There is no difference in the standard deviation of the minor axis length / major axis length before and after the surface coating treatment, and the volume resistance value is 2 × 10 ⁷
Ωcm.

Table 1 shows the magnetic particles for charging used in this example and the manufacturing conditions of the magnetic particles for charging used in each of the following Examples and Comparative Examples. Table 2 shows substance names corresponding to the abbreviations of the first and second surface coating agents used in Table 1.

[0169]

[Table 1]

[0170]

[Table 2] Next, a method for evaluating the charging magnetic particles will be described.

Using the digital copying machine described above, the digital magnetic copying machine was mounted on a charging device such that the coating density of the magnetic particles for charging became 180 mg / cm ^2, and the image carrier was mounted. In order for the coating density to reach the above value, a minimum of about 30 g of magnetic particles for charging is required. The magnetic brush charger was rotated in the opposite direction at the contact portion with the image carrier. At this time, the rotational peripheral speed of the charging device was 240 mm / s.

The evaluation conditions were as follows. First, the bias applied to the charging device was a DC voltage of -700 V and 1 KH
z, a rectangular wave oscillation voltage of 700 Vpp was applied. Temperature and humidity were measured under the conditions of 15 ° C./20% relative humidity. The developing bias is 1000 to the DC component of -500V.
A rectangular wave of Vpp / 3 KHz was superimposed.

Using a yellow developer, a 17-gradation image was copied. Thereafter, the image ratio was 0%, that is, the solid white image was copied 5 times in the 1000-sheet mode under the rotation peripheral speed of 300 mm / s, that is, after 5,000 copies, and a 17-gradation image was output as in the initial stage. The difference in color space between the yellow image before and after the endurance was evaluated.

In the evaluation, color laser copier paper (Canon Sales Co., Ltd.) was used.
SP68SPECTROPHOTOMETER (X-R
itemInc. L ^* (brightness) a ^* (red-
(Green) b ^* (yellow-blue) was measured. At this time, L ^{* is set} to 92.8.
17 gradations are selected so that 0 ± 0.10.
The difference between the initial ^* and after 5000 sheets was taken. This difference is represented by Δb ^* . The smaller the Δb ^* is, the smaller the change in hue is, which is preferable from the viewpoint of a color image.

The magnetic particles for charging 1, the above yellow developer,
And evaluation using the above photoreceptor, Δb ^* =
It was 2. Table 3 shows the evaluation results.

Example 2 A fixed-tank type mixer equipped with a stirrer and a heating means was kept at 100 ° C.
Then, a toluene solution in which 0.3 parts by mass of isopropoxytitanium tristearate was dissolved as a first surface coating agent, and the mixture was heated to 180 ° C., dried, and then allowed to cool.
Next, an ethanol solution in which 0.3 parts by mass of dodecyltrimethoxysilane was dissolved as a second surface coating agent was added, and 70
The temperature was raised to ℃ and dried to obtain charging magnetic particles 2. The heating loss of the charging magnetic particles 2 was 0.5% by mass. In addition,
It was understood that isopropoxytitanium tristearate was brownish cloudy and insoluble in ethanol.

There is no difference in the standard deviation of the minor axis length / major axis length before and after the surface coating treatment, and the volume resistance value is 5 × 10 ⁷
Ωcm.

The charging magnetic particles 2 were evaluated in the same manner as in Example 1. Table 3 shows the results.

Example 3 A fixed-tank type mixer equipped with a stirrer and a heating means was kept at 100 ° C.
Then, a toluene solution in which 0.3 parts by mass of isopropoxytitanium tristearate was dissolved as a first surface coating agent, and the mixture was heated to 180 ° C., dried, and then allowed to cool.
Further, an ethanol dispersion in which 0.3 parts by mass of n-propyltrimethoxysilane was dispersed as a second surface coating agent was added, the temperature was increased to 70 ° C., and the mixture was dried to obtain magnetic particles 3 for charging. The heating loss of the magnetic particles for charging 3 was 0.4% by mass.

There is no difference in the standard deviation of the minor axis length / major axis length before and after the surface coating treatment, and the volume resistance value is 6 × 10 ^7.
Ωcm.

The charging magnetic particles 3 were evaluated in the same manner as in Example 1. Table 3 shows the results.

Example 4 Charging magnetic particles 4 were obtained in the same manner as in Example 3 except that toluene was used instead of ethanol. There was no difference in the standard deviation of the ratio of the minor axis length / major axis length before and after the surface coating treatment, and the volume resistivity was 6 × 10 ⁷ Ωcm.

The charging magnetic particles 4 were evaluated in the same manner as in Example 1 above. Table 3 shows the results. Δb ^*
Was slightly higher at 10. It is considered that this is because, when the second surface coating layer was formed, toluene in which isopropoxytitanium tristearate as the first surface coating agent was soluble was used as a solvent.

Example 5 A fixed-tank type mixer equipped with a stirrer and a heating means was kept at 100 ° C.
Parts by mass and a toluene solution in which 0.3 parts by mass of isopropoxytitanium tristearate was dissolved as the first surface coating agent were added, and while removing toluene, the mixture was heated to 180 ° C. and dried, and then allowed to cool. Next, n is used as a second surface coating agent.
An ethanol solution in which 0.05 parts by mass of -propyltrimethoxysilane was dissolved was added, the temperature was raised to 70 ° C, and the mixture was dried to obtain magnetic particles 5 for charging. The heating loss of the magnetic particles for charging 5 was 0.3% by mass.

There is no difference in the standard deviation of the minor axis length / major axis length before and after the surface coating treatment, and the volume resistance value is 4 × 10 ⁷ Ω.
cm.

The charging magnetic particles 5 were evaluated in the same manner as in Example 1. Table 3 shows the results.

Example 6 A fixed-tank type mixer equipped with a stirrer and a heating means was kept at 100 ° C.
Parts by weight of aluminum 9-octadecenyl acetoacetate diisopropoxide 0.3 as a first surface coating agent
A toluene solution in which parts by mass were dissolved was added, and the mixture was heated to 180 ° C. and dried, and then allowed to cool. Next, a methanol solution in which 0.3 part by mass of n-propyltrimethoxysilane was dissolved was added, the temperature was raised to 70 ° C., and the mixture was dried to obtain magnetic particles 6 for charging. The loss on heating of the charging magnetic particles 6 was 0.4% by mass. In addition, aluminum 9-octadecenyl acetoacetate diisopropoxide was found to be cloudy and insoluble in methanol.

There is no difference in the standard deviation of the minor axis length / major axis length before and after the surface coating, and the volume resistance value is 5 × 10 ⁷ Ωc.
m.

The charging magnetic particles 6 were evaluated in the same manner as in Example 1. Table 3 shows the results.

<Example 7> Charging magnetic particles 7 were obtained in the same manner as in Example 6 except that magnetic particles 2 were used instead of magnetic particles 1. There was no difference in the standard deviation of the minor axis length / major axis length before and after the surface coating treatment, and the volume resistivity was 4 × 10 ⁷ Ωcm.

The charging magnetic particles 7 were evaluated in the same manner as in Example 1. Table 3 shows the results.

<Example 8> Charging magnetic particles 9 were obtained in the same manner as in Example 6 except that the magnetic particles 4 were used in place of the magnetic particles 1. There was no difference in the standard deviation of the minor axis length / major axis length before and after the surface coating treatment, and the volume resistivity was 3 × 10 ⁹ Ωcm.

Since the resistance of the magnetic particles for charging was high, the applied DC voltage was -950 V and the potential of the image carrier was -700 V
The charging magnetic particles 9 were evaluated in the same manner as in Example 1 except that the above-mentioned conditions were satisfied. Table 3 shows the results.

<Example 9> Charging magnetic particles 10 were obtained in the same manner as in Example 6 except that the magnetic particles 5 were used instead of the magnetic particles 1. There was no difference in the standard deviation of the minor axis length / major axis length before and after the surface coating treatment, and the volume resistivity was 3 × 10 ⁸ Ωcm.

The charging magnetic particles 10 were evaluated in the same manner as in Example 1. Table 3 shows the results.

<Example 10> Charging magnetic particles 11 were obtained in the same manner as in Example 6 except that magnetic particles 6 were used instead of magnetic particles 1. There was no difference in the standard deviation of the minor axis length / major axis length before and after the surface coating treatment, and the volume resistivity was 7 × 10 ⁶ Ωcm.

The charging magnetic particles 11 were evaluated in the same manner as in Example 1. Table 3 shows the results.

Example 11 A fixed-tank type mixer equipped with a stirrer and a heating means was kept at 100 ° C.
0 parts by mass and an ethanol solution in which 0.3 parts by mass of n-octyltrimethoxysilane were dissolved as the first surface coating agent were charged, heated to 120 ° C., dried, and then allowed to cool. Next, an ethanol solution in which 0.3 parts by mass of n-propyltrimethoxysilane was dissolved as a second surface coating agent was added, the temperature was raised to 70 ° C., and the mixture was dried to obtain magnetic particles 12 for charging. The heating loss of the charging magnetic particles 12 was 0.5% by mass.

There is no difference in the standard deviation of the minor axis length / major axis length before and after the surface coating treatment, and the volume resistance value is 9 × 10 ⁶
Ωcm.

The charging magnetic particles 12 were evaluated in the same manner as in Example 1. Table 3 shows the results.

Example 12 A fixed tank type mixer equipped with a stirrer and a heating means was kept at 100 ° C.
0 parts by mass and an ethanol solution in which 0.3 parts by mass of n-propyltrimethoxysilane was dissolved as the first surface coating agent were added, the temperature was increased to 120 ° C., and the mixture was allowed to cool and then allowed to cool. Next, an ethanol solution in which 0.3 part by mass of n-propyltrimethoxysilane was dissolved as a second surface coating agent was added, the temperature was increased to 70 ° C., and the mixture was dried to obtain magnetic particles 13 for charging. The loss on heating of the charging magnetic particles 13 was 0.5% by mass.

There is no difference in the standard deviation of the minor axis length / major axis length before and after the surface coating treatment, and the volume resistance value is 5 × 10 ⁹
Ωcm.

The charging magnetic particles 13 were evaluated in the same manner as in Example 1. Table 3 shows the results. Δb
^Although the value of ^* was slightly higher at 14, it was in a range where there was no problem in practical use. This is because n-propyltrimethoxysilane of the first and second surface coating agents was a compound having an alkyl chain having 3 carbon atoms, and the first surface coating agent was formed when the second surface coating layer was formed. It is considered that n-propyltrimethoxysilane was used as a solvent in which ethanol was soluble.

Example 13 A fixed-tank type mixer equipped with a stirrer and a heating means was kept at 100 ° C.
0 parts by mass and an ethanol solution in which 1.0 part by mass of n-propyltrimethoxysilane was dissolved as the first surface coating agent were added, the temperature was raised to 120 ° C., and the mixture was allowed to cool and then allowed to cool. Next, an ethanol solution in which 1.0 part by mass of n-propyltrimethoxysilane was dissolved as a second surface coating agent was added, the temperature was increased to 70 ° C., and the mixture was dried to obtain magnetic particles 14 for charging. The heating loss of the magnetic particles for charging 14 was 1.7% by mass.

There is no difference in the standard deviation of the minor axis length / major axis length before and after the surface coating treatment, and the volume resistance value is 4 × 10 ⁹
Ωcm.

The charging magnetic particles 14 were evaluated in the same manner as in Example 1. Table 3 shows the results. Δb
The value of ^* was slightly higher at 12. This is the first, second
The second reason is that n-propyltrimethoxysilane as the surface coating agent was a compound having an alkyl chain having 3 carbon atoms.
It is considered that ethanol used to dissolve n-propyltrimethoxysilane as the first surface coating agent was used as a solvent during the formation of the surface coating layer.

<Embodiment 14> In Embodiment 1, Δb ^*
After the evaluation of, a durability test was performed on 50,000 sheets of character images having an image ratio of 4%. Table 3 shows the results. The image quality of the yellow solid image was good, and an image with little fog was obtained. The amount of contamination was 0.08% by mass.

Here, the amount of contamination refers to the mass loss of the magnetic particles for charging before evaluation from the mass reduction of the magnetic particles for charging at a temperature of 150 ° C. to 400 ° C. in a nitrogen atmosphere in the analysis using a thermobalance. Is expressed as a percentage with respect to the sample amount (the amount of the magnetic particles for charging).

<Embodiment 15> In Embodiment 7, Δb ^*
After the evaluation of, a 50,000-sheet character image with an image ratio of 4% was subjected to an endurance test. As a result, a good yellow solid image and an image with little fog were obtained. Pollution amount is 0.35% by mass
It is. Table 3 shows the results.

<Embodiment 16> In the embodiment 8, Δb ^*
After the evaluation of, a durability test was performed on 50,000 sheets of character images having an image ratio of 4%. Table 3 shows the results. This is an image in which the unevenness of the charged potential of the photosensitive member due to the high resistance value of the magnetic particles is large and the fog is large. However, the yellow solid image was good. The contamination amount after running 50,000 sheets was 0.10% by mass, which was a good result.

Embodiment 17 In the image forming apparatus shown in FIG. 3, the charging magnetic particles 1 are used in the charging device of Pa, and the developing device is filled with the yellow toner and the developer.
The charging magnetic particles 1 were used for the charging devices of c and Pd, and the developing devices were filled with magenta, cyan, black toner and developer, respectively. Red, green, and violet were output as yellow, magenta, cyan, and their secondary colors. When a durability test was performed on 1,000 sheets, good color images were obtained from the initial stage to 1,000 sheets.

Comparative Example 1 A fixed-tank type mixer equipped with a stirrer and a heating means was maintained at 100 ° C.
Parts by mass and an ethanol solution in which 0.3 parts by mass of n-octyltrimethoxysilane and 0.3 parts by mass of n-propyltrimethoxysilane were dissolved as a surface coating agent, and heated to 70 ° C. and dried. Magnetic particles for charging 15 were obtained. The loss on heating of the magnetic particles for charging 15 was 0.4% by mass.

There is no difference in the standard deviation of the minor axis length / major axis length before and after the surface coating treatment, and the volume resistance value is 3 × 10 ⁹
Ωcm.

The charging magnetic particles 15 were evaluated in the same manner as in Example 1. Table 3 shows the results. Δb
The value of ^* was large and good results could not be obtained.

Comparative Example 2 A fixed-tank type mixer equipped with a stirrer and a heating means was kept at 100 ° C.
Parts by mass and an ethanol solution in which 0.6 parts by mass of n-propyltrimethoxysilane were dissolved were added, the temperature was raised to 70 ° C., and the mixture was dried to obtain magnetic particles 16 for charging. The heat loss of the magnetic particles 16 for charging was 0.4% by mass.

There is no difference in the standard deviation of the minor axis length / major axis length before and after the surface coating treatment, and the volume resistance value is 5 × 10 ⁹
Ωcm.

The charging magnetic particles 16 were evaluated in the same manner as in Example 1. Table 3 shows the results. Δb
The value of ^* was large and good results could not be obtained.

Comparative Example 3 A fixed-tank type mixer equipped with a stirrer and heating means was maintained at 100 ° C.
Parts by mass and an ethanol solution in which 2.0 parts by mass of n-propyltrimethoxysilane were dissolved were added, heated to 70 ° C. and dried to obtain magnetic particles 17 for charging. The heating loss of the charging magnetic particles 17 was 1.8% by mass.

There is no difference in the standard deviation of the minor axis length / major axis length before and after the surface coating treatment, and the volume resistance value is 5 × 10 ⁹
Ωcm.

The charging magnetic particles 16 were evaluated in the same manner as in Example 1. Table 3 shows the results. Δb
The value of ^* was large and good results could not be obtained.

Comparative Example 4 Evaluation was performed in the same manner as in Example 1 except that the magnetic particles 3 were used as magnetic particles for charging. Table 3 shows the results. The value of Δb ^* was large, and good results were not obtained.

<Comparative Example 5> Charging magnetic particles 8 were obtained in the same manner as in Example 6 except that the magnetic particles 3 were used instead of the magnetic particles 1. There was no difference in the standard deviation of the minor axis length / major axis length before and after the surface coating treatment, and the volume resistivity was 8 × 10 ³ Ωcm.

A charging method was performed in the same manner as in Example 1 except that a protection resistance of 0.5 MΩ was applied in series between the charging device and the high-voltage power supply to suppress pinhole leakage due to low resistance of magnetic particles. The magnetic particles 8 for use were evaluated.
Table 3 shows the results. During the solid white image output, a leak phenomenon around the drum pinhole due to low resistance was observed.

<Comparative Example 6> In Comparative Example 5, after the evaluation of Δb ^*, a durability test was performed on 50,000 character images having an image ratio of 4%. Table 3 shows the results. When the number of copies exceeded 20,000 in the durability test, the fog increased slightly. The evaluation for the yellow solid image was good. The contamination amount at 20,000 sheets was 0.55% by mass. This is because the standard deviation of the minor axis / major axis length is 0.06.

[0225]

[Table 3]

[0226]

According to the present invention, it is possible to provide a charging particle, a charging member, an image forming apparatus, and a process cartridge having excellent durability. Further, it is possible to provide an image forming apparatus and a process cartridge with less scraping of the photoconductor.

Further, according to the present invention, it is possible to provide a magnetic particle, a charging member, an image forming apparatus, and a process cartridge capable of obtaining a clear image for a long time even in full-color image formation. Furthermore, according to the present invention,
It is possible to provide a method for producing magnetic particles for charging, which has excellent durability, has less scraping of the photoreceptor, and can provide a stable full-color image for a long period of time.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically illustrating an example of an apparatus for measuring a volume resistance value according to the present invention.

FIG. 2 is a schematic diagram illustrating a configuration of a digital copying machine as an image forming apparatus of the present invention.

FIG. 3 is a schematic diagram of a full-color image forming apparatus that can preferably use the charging magnetic particles of the present invention.

FIG. 4 is a schematic diagram of a full-color image forming apparatus that can preferably use the charging magnetic particles of the present invention.

FIG. 5 is a schematic view of a full-color image forming apparatus that can preferably use the charging magnetic particles of the present invention.

[Explanation of symbols]

 Reference Signs List 201 Image fixing device 202 Magnetic brush charging device 203 Charging magnetic particles 204 Conductive sleeve (magnet) 205 Image carrier 206 Exposure device 207 Developer carrier 208 Developing device 209, 210 Stirring screw 211 Developer 212 Paper transport guide 213 Transfer material 214 Transfer roller 215 Paper transport belt 216 Transfer device 217 Process cartridge 218 Developing cartridge

Claims (21)

[Claims] 1. A charging magnetic particle that charges an image carrier by being rubbed against an image carrier on which an electrostatic latent image is formed, wherein the charging magnetic particle comprises a magnetic particle and a first surface. A first surface coating layer containing a coating agent and coating the surface of the magnetic particles;
A second surface coating layer that contains a surface coating agent and covers the surface of the first surface coating layer, and the charging magnetic particles include charging magnetic particles having a maximum chord length of 5 μm or more; The ratio of the minor axis length to the major axis length (minor axis length / major axis length) of the charging magnetic particles having a maximum chord length of 5 μm or more has a standard deviation of 0.08 or more. Magnetic particles for charging. 2. The magnetic particles for charging include magnetic particles for charging having a maximum chord length of 5 to 20 μm.
2. The charging magnetic particle according to claim 1, wherein the standard deviation of the short axis length / the long axis length of the charging magnetic particle having a maximum chord length of μm is 0.08 or more. 3. The magnetic particles for charging according to claim 2, wherein the standard deviation of the ratio of the minor axis length / major axis length is 0.10 or more. 4. An average particle diameter of the magnetic particles for charging is 10 to 10.
The charging magnetic particle according to any one of claims 1 to 3, which has a thickness of 200 µm. 5. The charging magnetic particle according to claim 4, wherein the average particle size is 15 to 30 μm. 6. The charging device according to claim 1, wherein at least one of the first surface coating agent and the second surface coating agent is a compound having an alkyl chain having 6 or more carbon atoms. Magnetic particles. 7. The magnetic particles for charging according to claim 1, wherein at least one of the first surface coating agent and the second surface coating agent is a coupling agent. 8. The charging magnetic particles having a volume resistance of 10
The charging magnetic particle according to any one of claims 1 to 7, wherein the magnetic particle has a particle diameter of ⁴ to 10 ⁹ Ωcm. 9. The charging magnetic particle according to claim 1, wherein the image carrier has a charge injection layer on a surface. 10. A method for producing magnetic particles for charging which charges an image carrier by rubbing against an image carrier on which an electrostatic latent image is formed, comprising: a step of crushing the magnetic particles; Forming a first surface coating layer by coating the surface of the magnetic particles with a first surface coating agent, and forming a second surface coating by coating the surface of the formed first surface coating layer with a second surface coating agent A method for producing magnetic particles for charging, comprising a step of forming a surface coating layer. 11. The charging magnetic particle contains a charging magnetic particle having a maximum chord length of 5 μm or more, and the short axis length and the long axis length of the charging magnetic particle having a maximum chord length of 5 μm or more. Standard deviation of the ratio (short axis length / long axis length) is 0.08
The method for producing magnetic particles for charging according to claim 10, which is as described above. 12. The charging magnetic particles have a particle size of 5 to 20 μm.
The magnetic particles for charging having a maximum chord length of
The short axis length of the charging magnetic particles having a maximum chord length of 0 μm /
The method for producing magnetic particles for charging according to claim 11, wherein the standard deviation of the major axis length is 0.08 or more. 13. The method for producing magnetic particles for charging according to claim 12, wherein the standard deviation of the short axis length / the long axis length is 0.10 or more. 14. The charging magnetic particles having an average particle size of 10
The method for producing magnetic particles for charging according to any one of claims 10 to 13, wherein the thickness is from 200 to 200 µm. 15. The method for producing magnetic particles for charging according to claim 14, wherein the average particle size is 15 to 30 μm. 16. The charging device according to claim 10, wherein at least one of the first surface coating agent and the second surface coating agent is a compound having an alkyl chain having 6 or more carbon atoms. A method for producing magnetic particles. 17. The method according to claim 1, wherein at least one of the first surface coating agent and the second surface coating agent is a coupling agent.
A method for producing the magnetic particles for charging according to any one of 0 to 16. 18. The charging magnetic particles having a volume resistance of 1
0 ⁴ 10 ⁹ manufacturing method of magnetic particles for charging according to any one of claims 10 to 17 which is [Omega] cm. 19. A charging member for charging an image carrier by rubbing the image carrier on which an electrostatic latent image is formed, wherein a magnetic force is applied to a magnet having a conductor to which a voltage is applied by a magnetic force. A charging member comprising the magnetic particles for charging according to any one of claims 1 to 9 carried thereon. 20. An image carrier on which an electrostatic latent image is formed, and a magnet body having a conductor to which a voltage is applied.
A charging device for charging the image carrier by bringing a charging member, which carries the magnetic particles for charging according to any one of claims 9 to 9 by magnetic force, into contact with the image carrier, and charging by the charging device An exposure device that forms an electrostatic latent image by exposing the surface of the image carrier thus formed, a developing device that visualizes the electrostatic latent image formed on the surface of the image carrier by toner, and a developing device that visualizes the electrostatic latent image formed by the toner. An image forming apparatus comprising: a transfer device that transfers a toner image to a transfer material. 21. A process cartridge used in an image forming apparatus for forming an image by visualizing an electrostatic latent image formed on an image carrier with toner and transferring the visualized image to a transfer material. 2. The method according to claim 1, further comprising the step of:
A charging member carrying the magnetic particles for charging according to any one of claims 1 to 9 by magnetic force, an image carrier on which an electrostatic latent image is formed, and an electrostatic latent image formed on the surface of the image carrier. A developing device for visualizing an image with toner,
And at least one member selected from the group consisting of a cleaning device that removes residual toner on the image carrier after being visualized by the toner, is integrally supported, and is detachably attached to the image forming apparatus main body. Process cartridge.