JPH11212332A - Image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming method which uses magnetic grains for electrifying more excellent in durability and which is stable prolonging over a long term by loading a cleanerless system using an electrifying magnetic brush. SOLUTION: This image forming method is constituted of a process that a photoreceptor provided with a photoreceptive layer on digital copying machine conductive support and an electric charge injection layer being most distant from the conductive supporting layer is electrified by bringing an electrifying member consisting of the magnetic grains into contact with the photoreceptor and applying a voltage, a process that a latent image is formed by exposing the photoreceptor and a process that the latent image is visualized by toner. Then, the DC voltage obtained by superimposing a vibration voltage whose interpeak is <=1,000 V is used as the voltage applied on the electrifying member. Besides, the average grain size of the magnetic grains is >=10 μm and <=40 μm and a ration between the minor axis length and the major axis length of the magnetic grains whose grains size is 5 μm to 20 μm is <=0.85. Besides, the volume resistance value of the whole magnetic grains is 10<4> to 10<9> Ωcm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic particle used for a member for charging an object and an image forming method using the charged member, and is applied to a copying machine, a printer, a facsimile and the like.

[0002]

2. Description of the Related Art Conventionally, many methods have been known as electrophotography, but generally, a photoconductive substance is used,
An electric latent image is formed on the photoreceptor by various means, and then the latent image is developed with toner to form a visible image.If necessary, the toner image is transferred to a transfer material such as paper. The toner image is fixed on the transfer material by pressure, 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 such a photosensitive member charging means in electrophotography, there is a so-called corotron or scorotron charging method utilizing corona discharge. further,
A charging method in which the generation of ozone is suppressed as much as possible by developing a charging member such as a roller, a fur brush or a blade into contact with the surface of the photoreceptor and forming a discharge in a narrow space near the contact portion has been developed and has been put to practical use.

However, in the charging method using corona discharge, a large amount of ozone is generated when corona discharge, particularly negative or positive corona, is generated. Therefore, it is necessary to provide an electrophotographic apparatus with a filter for capturing ozone. There is
There were problems such as an increase in the size of the device or an increase in running costs.

[0005] Further, among charging methods in which generation of ozone is suppressed as much as possible by forming a discharge in a narrow space, a method of charging by contacting with a photoreceptor, such as a blade or roller charging method, is used. Problems such as toner fusion tend to occur.

For this reason, a method of using a photoconductor in close proximity to the photoconductor to avoid direct contact has been studied. As the member for charging the photoreceptor, the above-described roller or blade or brush, a member obtained by applying a resistive layer to an elongated conductive plate-like material, and the like, there is a problem that it is difficult to control the proximity distance. There were difficulties in putting it to practical use.

For this reason, a technique of using a so-called magnetic brush, which has a relatively small contact load on the photoreceptor and holds magnetic particles with a magnet, as a charging member, has been studied.

[0008] 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 on the 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.

Japanese Patent Application Laid-Open No. S59-133569 discloses magnetic particles used as a charging member. A method in which particles coated with iron powder are held on a magnet roll and charged by applying a voltage to the magnetic particles. For improvement,
JP-A-7-72667 discloses that magnetic particles coated with a styrene acrylic resin or the like are also used.

However, as a remaining problem of these techniques, there is a problem that it is difficult to obtain stable charging properties during continuous use. For example, as proposed in Japanese Patent Application Laid-Open No. A configuration has been proposed in which toner is replenished so as to keep the amount of toner present in the brush constant, thereby stabilizing resistance. All of the above methods use a discharge phenomenon in a minute gap, and have a problem that the surface of the photoreceptor is damaged by a product generated by the discharge, and the image is likely to be deteriorated or image flow under high temperature and high humidity. It still remained.

Further, Japanese Patent Application Laid-Open No. Hei 6-258918 discloses that 30 to ¹⁰⁰ μm, which is 10 ⁸ to 10 ¹⁰ Ωcm.
m and 30 to 100 μm which is 10 ⁸ Ωcm or less.
a mixture of m and is the particle to the charging particles, in the Japanese Patent Laid-Open 06-274005 discloses, ⁵ × 10 5 Ω
It is disclosed that particles having a particle size of at least 5 cm and particles having a particle size of 5 × 10 ⁴ or less are mixed and used as charging particles. Has been proposed in the form of a mixture.

[0013] These have good electric resistance due to the particle size and resistance of the particles to be mixed, but if the particle size of the mixed particles is relatively close and the resistance is far away, the particles with low resistance are exposed during use. Since it gathers on the body surface, even if it has good pinhole resistance in the initial stage, it tends to cause pinhole leakage during use. Also, if the particle size is far,
Although the separation tendency of particles having low resistance can be suppressed, there is a problem that particles having low resistance are particularly likely to leak out in a low humidity environment.

Further, Japanese Patent Application Laid-Open No. Hei 8-6355 proposes a mixture of magnetic particles having a smooth surface and magnetic particles having an irregular surface. Japanese Patent Application Laid-Open No. 8-69156 discloses that In a method of forming a resin layer, Japanese Patent Application Laid-Open No. 8-69149, it is proposed that the particle size distribution of the magnetic particles for charging has a plurality of peaks. In these, the effect of extending the durability is described, but further improvement in the durability is desired.

Although various proposals have been made, as far as the present inventor can know, in the sense of practical use, a magnetic brush is used as a photosensitive member charging member in an electrophotographic apparatus such as a copying machine on the market. There are no examples done.

As described above, with respect to magnetic particles as a photosensitive member charging member, it has been insufficient to study the desirable physical properties and their effects from the viewpoint of physical properties. It is desired to develop a suitable composition of the particles.

The cleaning process in electrophotography has conventionally used blade cleaning, fur brush cleaning, roller cleaning, and the like. Either method mechanically scrapes off the transfer residual toner,
Alternatively, it is dammed and collected in a waste toner container. Therefore, there has been a problem that such a member is pressed against the surface of the photoconductor. For example, it has been suggested that the photoreceptor is worn down by strongly pressing the member to shorten the life of the photoreceptor. In fact, from the viewpoint of the apparatus, the provision of such a cleaning apparatus inevitably increases the size of the apparatus, which has been a bottleneck when aiming for a more compact apparatus.

For the above reasons, there has been a demand for a system which is not waste toner in terms of effective use of toner from the viewpoint of miniaturization of the apparatus and ecology.

A technique conventionally known as simultaneous cleaning or cleanerless development is disclosed in JP-A-59-133.
573, JP-A-62-203182, JP-A-63-133179, JP-A-64-20587
JP, JP-A-2-51168, JP-A-2-30
No. 2772, Japanese Patent Application Laid-Open No. 5-2287, Japanese Patent Application Laid-Open
Japanese Patent Laid-Open Nos. 2289, 5-53482, 5-61383, and the like. These known techniques use a corona, a brush, or a roller, and cannot satisfy all of the contamination of the surface of the photoreceptor by the discharge products, the nonuniform charging, and the like.

For this reason, a cleanerless technique using a so-called magnetic brush as a charging member, which has a relatively small contact load to the photosensitive member and holds magnetic particles by a magnet, has been studied.

For example, Japanese Patent Application Laid-Open No. Hei 4-21873 proposes an image forming apparatus which does not require a cleaning device by using a magnetic brush to which an AC voltage having a peak value exceeding a discharge limit value is applied. ing.
Furthermore, Japanese Patent Application Laid-Open No. Hei 6-118855 proposes an image forming apparatus equipped with a magnetic brush charging cleaning device without an independent cleaning device. Examples of magnetic particles used include iron, chromium, nickel, and cobalt. Such as metals or alloys or compounds thereof, triiron tetroxide, γ-ferric oxide, chromium dioxide, manganese oxide, ferrite, manganese-copper alloys and styrene resins, vinyl resins, ethylene resins, There are disclosures of particles coated with a rosin-modified resin, an acrylic resin, a polyamide resin, an epoxy resin, a polyester resin, or a resin containing magnetic fine particles dispersed therein.

However, the preferred form of the magnetic particles for charging is not disclosed, and a technical problem remains from the viewpoint of magnetic particles suitable for a cleanerless method.

[0023]

As described above, there has been a demand for an image forming method using magnetic particles for charging having a preferable configuration as a charging member. That is, there has been a demand for an image forming method that has stable charging properties during continuous use, can withstand long-term use, and has less load on the photoconductor.

Further, also in the cleanerless image forming method, there has been a demand for an image forming method which is stable in chargeability and suitably processes toner remaining after transfer.

An object of the present invention is to provide an image forming method using magnetic particles for charging, which is more durable than conventional ones.

Another object of the present invention is to provide an image forming method with less scraping of the photoreceptor.

Still another object of the present invention is to provide a stable image forming method for a long period of time by mounting a cleanerless system using a charged magnetic brush.

[0028]

According to the present invention, there is provided a photosensitive member having a photosensitive layer on a conductive support, and having a charge injection layer furthest from the conductive support layer, and a charging member comprising magnetic particles. Contacting and applying a voltage to charge the photoreceptor, exposing the photoreceptor to form a latent image, and visualizing the latent image with a toner, the method comprising: Voltage between peaks is 1000
V is a direct current voltage on which an oscillating voltage of not more than V is superimposed, the average diameter of the magnetic particles is 10 μm or more and 40 μm or less, and the ratio of the minor axis length / major axis length of the magnetic particles of 5 μm to 20 μm is 5 μm to 20 μm. , 0.85 or less, and the volume resistivity of the whole magnetic particles is 10 ⁴ to 10 ⁹ Ωcm.

According to a second aspect of the present invention, in the first aspect of the present invention, the volume resistance of the magnetic particles in the range of 5 μm to 20 μm is defined as Ra, and the volume resistance of the magnetic particles exceeding 15 μm is defined as Rb. At this time, 0.5 ≦ Ra / Rb ≦ 5.0.

Preferably, Ra / Rb satisfies 1.0 ≦ Ra / Rb ≦ 5.0.

The ratio of the minor axis length / major axis length of the portion exceeding 20 μm of the magnetic particles is 0.85 or less, and more preferably 0.80 or less.
The following is preferred.

The image forming method of the present invention does not include the step of transferring the visualized toner image to the transfer member and the independent cleaning step of cleaning the transfer residual toner on the photosensitive member. Can be included. Further, a photoconductor potential control member can be provided after the transfer step and before the charging step.

The photosensitive member potential control member is a member to which a voltage is applied, and is preferably applied to a polarity opposite to the charging polarity in the charging step.

Further, the magnetic particles have a size of 5 μm to 20 μm.
It is preferable that the ratio A of the minor axis length / major axis length of the particles of the part and the minor axis length / major axis length ratio B of the toner satisfy A <B.

The magnetic particles preferably have a heat loss of 0.5% by mass or less.

The surface of the magnetic particles may be treated with a coupling agent having a C6 or higher alkyl chain and having a central element of titanium, silicon, aluminum, or zirconium. The amount is 0.0001% by mass or more and 0.5% by mass or less.

According to the present invention, it is possible to obtain an image forming method which has stable chargeability during continuous use, has little environmental dependency, and has stable chargeability over a long period of time, especially in a cleanerless system.

Further, it is possible to realize an image forming method in which the load on the member to be charged is small and the whole system has high durability.

[0039]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

In general, as the magnetic particles for charging, various particles are described as possible as described in the prior art of the present application. However, according to the results of studies by the present inventors, magnetic particles as in the conventional example, as magnetic particles for photoreceptor charging, have many inadequate aspects, and as a result of intensive studies in view of the situation, The present invention has been accomplished by finding one of the preferred embodiments.

The magnetic particles used in the image forming method of the present invention have an average diameter of 10 μm to 40 μm.
m, and the shape of the magnetic particles is 5 μm to 2 μm.
The minor axis length / major axis length of the 0 μm portion is 0.85 or less, and the volume resistivity of the entire magnetic particle is 10 ⁴ to 10 ⁹ Ωcm.
Is a characteristic.

Such a configuration is more effective in durability than the conventional example. The cause of the deterioration in durability is that the magnetic particles surface is contaminated by toner or toner components mixed into the charging member or foreign matter such as paper powder, the resistance of the charging member increases, and the photoreceptor surface cannot be charged sufficiently. Met.

However, by adopting the structure of the present invention,
The following effects were confirmed.

1. Due to the deformed effect, the contact with the photoreceptor surface is improved.

2. By being deformed, the edge has an effect of cleaning the surface of the magnetic particles.

With the above effects, it has become possible to dramatically improve the durability as compared with conventional magnetic particles.

That is, the increase in resistance due to the adhesion of toner, paper dust, and other foreign matter mixed into the charging member can be suppressed, and preferable charging properties of the photosensitive member can be maintained.

Further, as another great effect, compared with the conventional example, the shape effect makes it possible to remarkably reduce the transfer residual toner passing through the charging member particularly in the cleanerless image forming method. It has been found that the effect of the residual toner on the image can be eliminated, a clear image can be obtained, and further, a longer life can be achieved.

A specific image defect caused by the transfer residual toner slipping through will be described by reversal development. The slipped toner blocks the image exposure light, causing a negative ghost.

2. For example, the fogged toner may not be charged at the contact point of the photoreceptor, resulting in a fogged image. However, in the configuration of the present invention, these can be remarkably improved.

The mechanism by which the functions and effects of the present invention can be obtained will be described below.

As the action relating to the shape of the magnetic particles and the toner as in the present invention, the interaction between the surface of the magnetic particles and the residual toner or toner component or the toner or toner component leaked from the cleaning step is considered. This is very important.

First, an example of a cleanerless image forming method will be described with reference to FIG.

The photoreceptor 12 charged by the magnetic brush charging device 11 composed of the magnet-containing nonmagnetic conductive sleeve 16 coated with the magnetic particles 15 forms a latent image by the exposing means 13. The latent image is reversely developed by a developing device 18 including, for example, a conductive non-magnetic sleeve 17 containing a developer 10 and a magnet.
An image visualized by toner is formed on the exposed portion above. The visualized image is transferred to a transfer material by the transfer unit 14, and the transfer residual toner exists on the photoconductor.
The toner remaining after the transfer is affected by the transfer, and the charge polarity is variously distributed from minus to plus.
The remaining transfer toner is charged to a desired polarity in the frictional charging of the magnetic particles and the toner constituting the magnetic brush while charging the photoreceptor while scraping the transfer residual toner with the magnetic brush charging device 11 that rotates and rubs. And the collection can be performed by the developing device.

At this time, the behavior of the contact portion between the photosensitive member 12 and the charging device 11 will be described with reference to FIG.

Magnetic particles obtained by sintering ferrite raw material aggregate particles formed by, for example, a spray-drying method can obtain ferrite particles which are relatively nearly spherical. The ferrite particles (22 in FIG. 2,
23, 24, 25, and 26) as a charging member, when a toner obtained by kneading and pulverizing a resin and a coloring powder is used, the transfer residual toner 27 is in a state of being firmly attached to the photoreceptor surface layer 21. Rushes into the charging member. It is considered that the reason for the strong attachment is that the material has a random shape due to the pulverization, and therefore, is in a state of being attached to the surface of the photoreceptor at many contact points.

On the other hand, it is possible to scrape off a part of the charging member, but due to its shape, particles in contact with the photoreceptor roll or remain as they are.
It is considered that the magnetic particles 23 in FIG. 2 ride on the transfer residual toner 27 that is firmly attached, pass through the state of the magnetic particles 24, reach the state of the magnetic particles 25, and the transfer residual toner slips through.

For the above reasons, in the case of FIG. 2, there is a tendency that a sufficient rubbing force to scrape off most of the transfer residual toner cannot be obtained.

On the other hand, a case where ferrite particles having irregular shapes are used and toner particles having a shape close to a true sphere obtained by a polymerization method or the like will be described with reference to FIG.

Transfer residual toner 3 when a spherical toner containing a colorant is used as a charging member using ferrite particles (32, 33, 34, 35 in FIG. 3) obtained by the pulverization method.
6, 37, and 38 enter the charging member in a state of being attached to the photoconductor surface layer 31. In this case, the transfer residual toner is spherical and adheres to the photoreceptor surface layer 31 at almost one point. On the other hand, ferrite particles having an irregular shape have relatively many contact points, and the ferrite particles 32, 33, and 34,35
The adhesive force between the toner and the photoreceptor surface layer 31 has many contact points, so that the adhesive force between the toner and the surface of the photoreceptor surface layer 31 exceeds the adhesive force, and the transfer residual toner is moved along the photoreceptor surface layer 31, The toner is taken into the charging member without being left on the surface layer 31 to prevent slippage.

Therefore, with respect to the shape of the magnetic particles used as the charging member and the toner used, it is possible to obtain a higher effect of preventing the slip-through phenomenon by making the magnetic particles irregular.

Further, the toner preferably has a particle diameter of 3 μm to 15 μm as a weight average particle diameter, but from 3 μm to 9 μm in order to faithfully reproduce a latent image.
μm is most preferably used.

In order to achieve a high effect of preventing the slip-through phenomenon, it is necessary that the shape of the magnetic particles close to or slightly larger than the toner particle diameter has a toner scraping effect.

That is, when the ratio of the minor axis length / major axis length of the particles of 5 μm to 20 μm is 0.85 or less, the scraping force of the transfer residual toner on the photosensitive member is high. The effect of preventing toner from slipping through is high. Preferably, 0.
80 or less, and 0.75 or less, the slip-through preventing effect is very high. On the other hand, if it is less than 0.5, the fluidity of the charging member will be extremely deteriorated and will not be practical. In this respect, it is preferably 0.6 or more.

Further, it is more effective that the ratio of the minor axis length / major axis length of the particles exceeding 20 μm is 0.85 or less.

Here, a method for separating a portion of 5 μm to 20 μm will be described. Prepare sieves having openings of 5 μm and 20 μm. These sieves have a size of Φ75 mm × H20 mm, and the method of forming the openings of 5 μm or 20 μm is to adjust the diameter of the sieve by plating to increase the wire diameter. Open from above, 25 μm, 20 μm, 5 μm
Are placed in this order, 0.5 g of magnetic particles are placed on a sieve having an aperture of 25 μm, and sufficient vibration is applied.
Collect m-on magnetic particles. Further, the particles remaining on the 5 μm sieve are further subjected to a differential pressure of 200 mmAq to remove particles in a 5 μm pass. This sample is used for measurement. Samples exceeding 20 μm are mixed with magnetic particles of 20 μm and 25 μm among the above sieves to obtain samples. In the case of magnetic particles, the ratio of the minor axis length / major axis length is, for example, FE-SEM manufactured by Hitachi, Ltd.
Using (S-800), 100 magnetic particle images magnified 500 times were randomly extracted, and based on the image information, image analysis was performed using, for example, Image Analyzer V10 (manufactured by Toyobo Co., Ltd.). Is the arithmetic mean of Alternatively, similarly, in the case of toner, 100 toner images having a size of 2 μm or more are randomly extracted from the 1000 times enlarged toner image, and the same analysis is performed.

The details of the analysis are as follows. First, from an electron microscope photograph, 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 details, refer to Image Analyzer
V10 (manufactured by Toyobo Co., Ltd.) has a detailed description, but if the method is briefly described, the ratio of the major axis to the minor axis of the ellipse is passed through a procedure of replacing the shape of the object with the ellipse. That is to take. The procedure is as follows. For the binarized shape of the magnetic particles or toner, a small area Δs = Δ at coordinates (u, v)
Assuming that the specific gravity of u · Δv is 1, the second moment about the horizontal axis and the vertical axis (through the horizontal axis and the vertical axis) with respect to the origin (X, Y) passes through the center of gravity of the binarized shape of the particle. The second moment Mx and the second moment My about the vertical axis are represented by Mx = ΣΣ (u−X) ² My = ΣΣ (v−Y) ² , and the synergistic moment of inertia Mxy is given by Mxy = ΣΣ (u −X) · (v−Y), and the angle Θ satisfying the following equation has two solutions.

[0069]

(Equation 1) Further, the moment of inertia in the axial direction forming an angle Θ with the horizontal axis is represented by MΘ = Mx · cos ² Θ + My · sin ² Θ−Mxy · sin 2 、. Done, M
The smaller of Θ is the main axis.

Further, on any axis,

[0071]

(Equation 2) When plotting the points corresponding to, these create an ellipse,
Assuming that this principal axis coincides with the principal axis of inertia, if the direction in which the value of MΘ takes a small value is A, and the larger one is B, the following ellipse is obtained.

A · x ² + B · y ² = 1 The ratio of the minor axis length / major axis length in the present invention is:

[0073]

(Equation 3) It is represented by

The average particle size and distribution of the magnetic particles were measured using a laser diffraction type particle size distribution analyzer HEROS (manufactured by JEOL Ltd.) by dividing the range of 0.05 μm to 350 μm into 32 logarithms, and the volume median diameter was 50%. Was used as the average particle size.

The volume ratio of the magnetic particles occupying 5 μm to 15 μm is preferably from 10% by volume to 70% by volume with respect to all the magnetic particles, and if it is less than 10, the durability and the effect of preventing slip-through are remarkable. On the other hand, if it exceeds 70% by volume, the movement of the particles becomes poor, and the uniformity of charging tends to be lost. More preferably, 15% by volume
Not less than 60% by volume. More preferably, it is 50% by volume or less.

When the volume ratio of the magnetic particles occupied by particles of 2 μm or less is 5% by volume or less, the leakage of the magnetic particles during use is small and the practicality is high. Further, more preferably, 2
% Volume or less is preferred.

Further, in the present invention, 5 μm to 15 μm
Of the channels divided as shown in Table 1 obtained by the laser diffraction type particle size distribution analyzer HEROS (manufactured by JEOL Ltd.) as shown in Table 1, 5.7 μm to 1
Add 3.5 μm and express as a percentage of the whole.
Similarly, as for the ratio of particles of 2 μm or less, the sum of the channel average values of 1.15 μm and 2.00 μm in Table 1 is expressed as a percentage of the whole.

In the present invention, a preferable range of the magnetic particles for charging is from 10 to 40 μm.
If it is smaller than m, the magnetic particles are likely to leak, and the magnetic particles are inferior in transportability when used as a magnetic brush. If it exceeds 40 μm, the charging uniformity of the injection charging method of the present invention tends to deteriorate. More preferably, it is 15 to 30 μm.

Further, as disclosed in JP-A-8-69149, adjusting the magnetic particles so as to provide two or more peaks in the particle size distribution may be used to make the present invention more effective. Can be. As an effect of providing two peaks, there is an effect of securing a conduction path, and a synergistic effect of durability can be obtained together with the shape effect in the present invention.

The definition of a plurality of peaks or shoulders in the present invention is as follows. In the measurement method using the above-mentioned laser diffraction type particle size distribution analyzer HEROS (manufactured by JEOL Ltd.), a channel having the largest volume ratio of each channel is used. The average value is used as the position of the main peak. further,
For the second and subsequent peaks or shoulders, the volume ratio of the channel of the main peak is 1 to
Those having a volume ratio of / 10 or more are defined as peaks or shoulders. If the ratio is smaller than 1/10, the effect is weakened. Preferably, for the main peak and the second and subsequent peaks or shoulders, 5 μm to 3 μm
The thickness is preferably set to 0 μm, or 20 μm to 60 μm.

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

Ferrite magnetic particles are easily deformed when pulverized, and are suitable materials for realizing the constitution of the present invention.

A preferred method of producing ferrite particles in the present invention is a method of pulverizing ferrite particles of 20 μm to 80 μm.

Further, after pulverization, classification is appropriately performed, and the powder can be used as it is. If necessary, it can be used by mixing with other magnetic particles.

In particular, when a structure having a plurality of peaks is used, a method in which the pulverizing step is adjusted so as to leave a peak having a large particle size and a peak on the low particle size side is preferably formed. Used.

Although a production method by pulverizing a mass of ferrite is also possible, it is preferable to pulverize ferrite particles from the viewpoint of efficiency.

As a conventional example, it is disclosed that magnetic particles obtained by kneading and pulverizing magnetite and a resin are used.
It tends to exceed 0.85 and contains a large amount of resin components, which tends to cause a large leakage of magnetic particles from the charging member.
Further, in the 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 there is a tendency that a sufficient effect of improving durability cannot be obtained.

The magnetic particles for charging used in the present invention have a volume resistance of 1 × 10 ⁴ Ωcm or more and 1 × 10 ⁹ Ω.
cm or less. If it is lower than 1 × 10 ⁴ Ωcm, pinhole leakage tends to occur, and 1 × 1
If it exceeds 0 ⁹ Ωcm, charging of the photoconductor becomes insufficient.

In terms of leakage of magnetic particles, the resistance value of the magnetic particles for charging is more preferably 1 × 10 ⁶ Ωcm or more.

The method of measuring the volume resistance of the magnetic particles is as follows. A cell A shown in FIG. 4 is filled with the magnetic particles, electrodes 41 and 42 are arranged in contact with the magnetic particles, and a voltage is applied between the electrodes. It was obtained by measuring the flowing current. The measurement conditions were as follows: the contact area between the filled magnetic particles and the electrode was 2 cm ² , the thickness was 1 mm, and the upper electrode was 10 kg in an environment of 23 ° C. and 65%.
The applied voltage is 100V. 43 is a guide ring, 44 is an ammeter, 45 is a voltmeter, 46 is a constant voltage device, 47 is a measurement sample, and 48 is an insulator.

Further, a major feature of the present invention is that the difference in resistance between particles having a relatively small particle size and particles having a relatively large particle size is small.

Preferably, 5 μm to 20 μm of the magnetic particles
The volume resistance value of the particles in the m part is Ra,
When the volume resistance value of the portion exceeding m is Rb, 0.5 ≦ Ra / Rb ≦ 5.0, and more preferably 1.0 ≦ Ra / Rb ≦ 5.0.

In measuring the volume resistivity of the magnetic particles of 5 μm to 20 μm and the portion exceeding 20 μm, the magnetic particles are separated as follows. 5μm and 20μ openings
Prepare m sieve. These sieves are Φ75mm
The size of the opening is 5 mm or 20 mm, and the size of the sieve is adjusted by, for example, enlarging the wire diameter of the sieve by plating or the like, if necessary. Sieves are opened in the order of 25 μm, 20 μm, and 5 μm in order from the top, and 0.5 g of magnetic particles are placed on a sieve having an opening of 25 μm and sufficiently vibrated to collect magnetic particles having a 20 μm pass and 5 μm on. Further, the particles remaining on the 5 μm sieve are further subjected to a differential pressure of 200 mmAq to remove particles in a 5 μm pass. This sample is used for measurement. 20μ
m of samples above 20
The magnetic particles on μm and 25 μm are mixed to form a sample.

When the resistance value of the particles having a relatively small particle size is lower than 1/10 of the resistance value of the particles having a relatively large particle size, when an oscillating voltage is applied to the charging member, particularly in a low humidity environment, This is because particles having a relatively small particle diameter and a low resistance have a strong tendency to fall off the charging member. In particular, in the case of the cleaner-less image forming method, the tendency to drop off is even stronger.

Furthermore, if particles having relatively close particle diameters and different resistance values by one digit or more are used in mixture, during use,
Particles having low resistance are biased toward the surface of the photoreceptor, and the bias of the low-resistance particles tends to cause pinhole leakage.

When the ratio of the minor axis length to the major axis length exceeds 0.8, the toner particles relatively easily move on the photoreceptor due to the rubbing of the magnetic particles. More preferably, it exceeds 0.90.

As the binder resin used in the toner of the present invention, a wide variety of resins known as binder resins for toner, such as styrene resins, polyester resins, acrylic resins, phenol resins and epoxy resins, may be used alone or in combination. Can be used.

As the colorant, conventionally known inorganic and organic dyes and pigments can be used. For example, carbon black, aniline black, acetylene black, naphthol yellow, hansa yellow, rhodun lake, alizarin lake, Bengala, phthalocyanine blue, indanthrene blue and the like. These are usually used in an amount of 0.5 to 20 parts by weight based on 100 parts by weight of the binder resin.

For the purpose of controlling charge, a nigrosine dye, a quaternary ammonium salt, a salicylic acid-based metal complex or metal salt, acetylacetone, or the like can be used.

To prepare the toner according to the present invention, for example, a binder resin, a wax, a metal salt or a metal complex,
Pigments, dyes, or magnetic substances as colorants, if necessary, a charge control agent, other additives, etc. are sufficiently mixed by a mixer such as a Henschel mixer or a ball mill, and then heated, rolled, kneaded, or extruded. The metal compounds, pigments, dyes, and magnetic materials are dispersed or dissolved in a resin mixed with each other by melt kneading using a heat kneader, and after cooling and solidifying, pulverization and classification are performed according to the present invention. However, the developer can be obtained.

The shape of the toner particles depends on the pulverizing and classifying step, and usually does not exceed 0.8. Therefore, in order to obtain a toner shape having a ratio of short axis length / long axis length of more than 0.8, and more preferably more than 0.9, surface treatment is performed mechanically and thermally to form the toner. Is preferably controlled. As a method of controlling the shape, a known method can be used. For example, Nara Machinery's hybridization system,
Hogkawa Micron Ongmill can be used. Further, a method of forming into a sphere by hot air, a method of forming into a sphere in a warm bath, a method of dissolving in a solvent and forming into a sphere by a spray drying method are also possible.

In the toner composition used in the present invention, an inorganic fine powder is preferably present on the surface. The following inorganic fine powder is used in the present invention. For example, colloidal silica, titanium oxide, iron oxide, aluminum oxide, magnesium oxide, calcium titanate, barium titanate, strontium titanate, magnesium titanate, cerium oxide, zirconium oxide, and the like can be used. These can be used alone or in combination of two or more.

It is preferable to use toner particles formed by a polymerization method as the toner particles having a ratio of the short axis length / the long axis length exceeding 0.9. In particular, since the toner particles formed by polymerizing the surface layer portion of the toner particles are generated by polymerizing the monomer composition in a dispersion medium, the surface of the toner particles can be obtained with a considerably smooth surface. .

JP-B-36-10231, JP-A-Showa 5
No. 9-53856, JP-A-59-61842, a method of directly producing toner particles from a polymerizable monomer composition using a suspension polymerization method, and a method of dissolving in a polymerizable monomer. A dispersion polymerization method in which toner particles are directly produced using an aqueous organic solvent in which the polymer obtained in step 1 is insoluble, and a soap-free method in which polymerizable monomers are directly polymerized in the presence of a water-soluble polar polymerization initiator to produce toner particles. It is possible to produce toner particles using an emulsion polymerization method such as a polymerization method.

When a direct polymerization method is used as a method for producing toner particles, a polymerization initiator such as 2,2 is used.
2'-azobis- (2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 1,
An azo or diazo polymerization initiator such as 1'-azobis (cyclohexane-1-carbonitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, azobisisobutyronitrile; Peroxide-based polymerization initiators such as benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide, and lauroyl peroxide are used. The amount of the polymerization initiator varies depending on the desired degree of polymerization, but is generally 0.1 to the weight monomer.
It is used in an amount of 5 to 20% by weight. The type of the polymerization initiator varies slightly depending on the polymerization method, but is used alone or in combination with reference to the 10-hour half-life temperature.

For controlling the degree of polymerization, known crosslinking agents, chain transfer agents, polymerization inhibitors and the like may be further added and used.

When the suspension polymerization is used for producing the toner, tricalcium phosphate, magnesium phosphate, aluminum phosphate, zinc phosphate, calcium carbonate, carbonate Magnesium, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium sulfate,
Barium sulfate, bentonite, silica, alumina and the like can be mentioned. Examples of the organic compound include polyvinyl alcohol, gelatin, methylcellulose, methylhydroxypropylcellulose, ethylcellulose, sodium salts of carboxymethylcellulose, starch and the like. It is preferable to use 0.2 to 10.0 parts by weight of these dispersants based on 100 parts by weight of the polymerizable monomer.

As these dispersants, commercially available ones may be used as they are, but in order to obtain finely dispersed particles having a uniform particle size, the fine particles of the inorganic compound are dispersed under high speed stirring in a dispersion medium such as water. May be generated. For example, in the case of tricalcium phosphate, under high-speed stirring, by mixing an aqueous sodium phosphate solution and an aqueous calcium chloride solution to produce tricalcium phosphate fine particles, a fine-grained dispersant suitable for suspension polymerization can be obtained. Can be.

In order to refine these dispersants, 0.00
You may use together 1-0.1 weight part of surfactants. Specifically, commercially available nonionic, anionic and cationic surfactants can be used. Examples include sodium dodecylbenzene sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, sodium oleate, sodium laurate, potassium stearate, calcium oleate, and the like.

In the case where a direct polymerization method is used to produce toner particles, the toner particles can be produced by the following production method.

A releasing agent comprising a low softening point substance, a colorant, a charge control agent, a polymerization initiator and other additives are added to the polymerizable monomer, and the mixture is uniformly dissolved or dispersed by a homogenizer, an ultrasonic disperser or the like. The allowed monomer composition is mixed with an ordinary stirrer or homomixer in an aqueous phase containing a dispersion stabilizer,
Disperse with a high shear stirrer such as a homogenizer. Preferably, the stirring speed and the stirring time are adjusted so that the droplets of the monomer composition have a desired size of the toner particles,
Granulate. After that, by the action of the dispersion stabilizer, stirring may be performed to such an extent that the particle state is maintained and the particles are prevented from settling. The polymerization temperature is 40 ° C. or higher, generally 50 to
The polymerization is preferably performed at a temperature of 90 ° C. The temperature may be raised in the latter half of the polymerization reaction, and further in the latter half of the reaction or in order to remove unreacted polymerizable monomers, by-products, etc. After completion, a part of the aqueous medium may be distilled off from the reaction system.
After the completion of the reaction, the generated toner particles are collected by washing, 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 composition.

The average particle size and the particle size distribution of the toner can be measured by a method using a Coulter Counter TA-II, Coulter Multisizer (manufactured by Coulter Inc.), or the like. In the present invention, a Coulter Multisizer (manufactured by Coulter) is connected to an interface (manufactured by Nikkaki) that outputs a number distribution and a volume distribution, and a PC9801 personal computer (manufactured by NEC). To prepare a 1% NaCl aqueous solution. For example, ISOTON R-II (manufactured by Coulter Scientific Japan) can be used. As a measurement method, 0.1 to 5 ml of a surfactant (preferably an alkylbenzene sulfonate) is added as a dispersant to 100 to 150 ml of the electrolytic aqueous solution, and 2 to 20 mg of a measurement sample is further added. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment for about 1 to 3 minutes by an ultrasonic disperser, and the volume of toner particles having a particle size of 2 μm or more is measured using the Coulter Multisizer with an aperture of 100 μm.
The number is measured to calculate a volume distribution and a number distribution. The volume-based weight average particle diameter (D4: the median value of each channel is a representative value of the channel) determined from the volume distribution, the weight variation coefficient (S4), and the number-based length average particle diameter determined from the number distribution ( D1), the length variation coefficient (S1), the weight-based coarse powder amount (particle diameter 8.00 μm or more) determined from the volume distribution, and the number-based fine powder amount (particle diameter 5 μm) determined from the number distribution.
m or less).

In order to make the present invention more effective, it is preferable that the magnetic particles of the present invention have been treated with a coupling agent having a structure in which 6 or more carbon atoms are linearly connected.

Since the magnetic particles for charging are rubbed tightly with the photoreceptor, there is a severe condition for shaving the photoreceptor, especially for an organic photoreceptor. As an effect by including the configuration of the present invention, lubrication is imparted by a long-chain alkyl group, which has an effect on photoreceptor damage and an effect on contamination of the surface of the magnetic particles for charging. Particularly, when the surface layer of the photoreceptor is made of an organic compound, it has a remarkable effect.

From this viewpoint, the alkyl group needs to be continuous with 6 or more carbon atoms, preferably 8 or more carbon atoms, and it is considered that about 30 or less carbon atoms are possible. When the number of the alkyl groups exceeds 30, it tends to be insoluble in a solvent, and it is difficult to uniformly treat the surface of the magnetic particles. Tend to be non-uniform.

The amount of the coupling agent is as follows.
0.0001% by mass or more and 0.5% or more based on the magnetic particles for charging.
% By mass or less is preferred. When the amount is less than 0.0001% by mass, the effect of the coupling agent is not observed, and when the amount exceeds 0.5% by mass, the flowability of the magnetic particles for charging is deteriorated, and the charging magnetic particles are not practically used. In this sense, more preferably 0.001
An amount of not less than 0.2% by mass and not more than 0.2% by mass can be preferably used.

In the present invention, it is basically desirable that the surface of the magnetic particles for charging is composed of only a coupling agent, but it is also possible to coat a small amount of a resin component. In this case, an amount equivalent to the amount of the coupling agent is preferable.

Further, it can be used in combination with resin-coated magnetic particles for charging. The mixing ratio in that case is preferably 50% by mass or less based on the mass of the magnetic particles in the charger. 50
If the amount is more than 10% by mass, the effect of the magnetic particles for charging of the present invention is weakened.

In this sense, the weight loss on heating is preferably 0.5% by mass, more preferably 0.2% by mass.
It is as follows.

Here, the heating loss refers to a temperature of 150 ° C. to 800 ° C. in a nitrogen atmosphere in an analysis using a thermobalance.
It is the amount of mass reduction up to.

As the coupling agent used in the present invention, a central element such as titanium, aluminum, silicon and zirconium may be used as long as it has a structure in which 6 or more carbon atoms are linearly linked to the hydrophobic group. Do not choose.

The coupling agent in the present invention 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.

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

The hydrophobic group may be any as long as it has a structure in which 6 or more carbon atoms are linearly connected in its structure. In the form of bonding with the central element, carboxylic acid esters, alkoxy, sulfone An acid ester, a phosphoric ester or a direct bond may be formed. Further, the structure may contain a functional group such as an ether bond, an epoxy group, or an amino group.

Specific examples of the compounds that can be used in the present invention include: (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

[0126]

Embedded image Further, when the coupling agent is present on the surface of the magnetic particles for charging of the present invention, the amount thereof is 0.5% by mass, preferably 0.2% by mass or less.
Since a resistance value substantially equal to that of magnetic particles not present on the surface can be obtained, the stability in production and the stability in quality are higher than in the case where a conductive particle-dispersed resin is used.

Further, the reaction rate of the coupling agent is 8
It is preferably 0% or more, and more preferably,
85% or more. This is because, in the present invention, since a coupling agent having a relatively long alkyl group is used, if the proportion of unreacted substances is large, the fluidity is deteriorated.
When the surface of the photoreceptor to be used is substantially a non-crosslinked resin, an unreacted processing agent may permeate the surface of the photoreceptor, and may cause clouding or fogging. For this reason, it is preferable to use a coupling agent that can react with the surface of the magnetic particles.

As a method for measuring the reaction rate of the coupling agent, a solvent capable of dissolving the coupling agent to be used may be selected, and the abundance before and after washing may be measured.

For example, the coupling agent component in the solvent is immersed in a solvent 100 times the amount of the treated magnetic particles, and the amount of the coupling agent component in the solvent is determined by chromatography. , ESCA, CH
Means for quantification by a method such as N, TGA, etc., and quantification of the abundance before and after washing are possible.

In the present image forming method, an injection charging method can be preferably used.

As the injection charging method, by using a photoreceptor in which the electrophotographic photoreceptor is furthest away from the support and has a charge injecting layer, 80
% Or more, and 90% or more. Therefore, a further ozoneless charging method can be realized in comparison with the charging method interpreted by Paschen's law. In this case, when the photoconductor has the charge injection layer farthest from the support, a potential of 90% or more of the applied voltage can be formed on the photoconductor by DC charging. More specifically, in order to satisfy the condition that sufficient chargeability and image deletion do not occur in the layer farthest from the support, a charge having a volume resistance value in the range of 1 × 10 ⁸ Ωcm × 1 × 10 ¹⁵ Ωcm. That is, a photoreceptor having an injection layer is used. More preferably, the volume resistance value is 1 × 1 in terms of image flow.
0 ¹⁰ Ωcm to 1 × 10 ¹⁵ Ωcm, and the volume resistance value is 1 × 10 ¹² Ωcm to 1 × 10 ¹⁵ Ω in consideration of environmental fluctuations.
cm is preferably used. In 1 × 10 ⁸ Ωcm smaller volume resistivity can not retain an electrostatic latent image, an image flow occurs particularly in high-temperature and high-humidity environment, 1 × 10 ¹⁵
If the resistance value is larger than Ωcm, the charge from the charging member cannot be sufficiently received, and the charging tends to be poor.

Further, in the image forming method of the present invention,
As the voltage applied to the photosensitive member charging member, it is preferable to apply an oscillating voltage. The effect of applying the oscillating voltage is that stable charging can be obtained against disturbances such as mechanical accuracy.

In the injection charging method, when an oscillating voltage is applied, the above-described advantages can be obtained. However, the applied oscillating voltage is limited, and is limited to 100 Hz to 10 Hz.
A frequency of about kHz is preferable, and the peak-to-peak voltage is
Preferably, the voltage is 1000 V or less. In the injection charging method, since the photoconductor potential follows the applied voltage, if the peak-to-peak voltage is too large, the potential of the photoconductor charging surface becomes wavy, which may cause fog or reversal fog. Because.

As for the oscillating voltage, the effective peak-to-peak voltage is 100 V or more, preferably 300 V or more.
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 can be made of a material having a medium resistance by dispersing an appropriate amount of light-transmitting and conductive particles in an insulating binder resin. Forming a layer is also an effective means. By providing such a functional layer surface, it serves to hold the charge injected from the charging member, and also serves to release the charge to the photoreceptor support during image exposure, thereby reducing the residual potential. Let it.

Here, the method for measuring the volume resistance of the charge injection layer is as follows: a charge injection layer is formed on polyethylene terephthalate (PET) having a conductive film deposited on the surface, and this is injected into a volume resistance measurement device (manufactured by Hewlett-Packard Company). 4140B
pAMATOR) at 23 ° C and 65% environment.
A voltage of 0 V was applied for measurement.

The particle size of the conductive particles is preferably 0.3 μm or less from the viewpoint of translucency, and most preferably 0.1 μm or less. It is 2 to 250 parts by mass, preferably 2 to 190 parts by mass, based on 100 parts by mass of the binder resin. If the amount is less than 2 parts by mass, it is difficult to obtain a preferable volume resistance value. If the amount exceeds 250 parts by mass, the film strength tends to decrease, and the charge injection layer tends to be scraped. The thickness of the charge injection layer is
Preferably 0.1 to 10 μm, optimally 1 to 7 μm
It is. Preferably, the charge injection layer contains a lubricant powder. The expected effect is that the friction between the photosensitive member and the charging member during charging is reduced, the nip involved in charging is enlarged, and the charging characteristics are improved. Also,
Since the releasability of the photoreceptor surface is improved, magnetic particles are less likely to adhere. In particular, as the lubricant particles, it is preferable to use a fluororesin, a silicone resin or a polyolefin resin having a low critical surface tension. Particularly preferably, a tetrafluoroethylene resin is used. 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 is less than 2 parts by mass, the amount of the lubricant powder is not sufficient, so that the effect of improving the chargeability of the photoreceptor is not sufficient, and the transfer residual toner tends to increase from the viewpoint of a cleanerless device. If the amount exceeds 50 parts by mass, the resolution of the image and the sensitivity of the photoreceptor tend to decrease.

When the surface layer is coated with an inorganic layer, the lower photoconductive layer is preferably amorphous silicon, and the blocking layer, photoconductive layer and charge injection layer are formed on the cylinder by glow discharge or the like. It is preferable to form them sequentially.

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 surface protective layer and the photosensitive layer. The purpose of such an intermediate layer is to enhance the adhesion between the protective layer and the photosensitive layer, or to function as a charge barrier layer. As the intermediate layer, for example, a commercially available resin material such as an epoxy resin, a polyester resin, a polyamide resin, a polystyrene resin, an acrylic resin, and a silicone resin can be used.

As the conductive substrate for the photoreceptor, a metal having aluminum, nickel, stainless steel, steel, or the like, a plastic having a conductive film, glass, conductive paper, or the like can be used.

Further, there is a preferable range in the triboelectric charging property between the toner used and the magnetic particles of the charging member.
The toner 7 used for the charging member magnetic particles 100
Is the same as the charging polarity of the photoconductor, and its absolute value is 1 to 90 mC / kg.
Preferably 5-80 mC / kg, more preferably 1
When it is 0 to 40 mC / kg, the characteristics of taking in and sweeping out toner and charging of the photoreceptor are good.

As a preferable measuring method, a mixture obtained by adding 0.000020 kg of toner to 0.040 kg of magnetic particles to be measured under an environment of 23 ° C. and 60% relative humidity is 50 to 1
Place in a 00 ml polyethylene bottle and shake by hand 150 times. A mixture of the toner to be used and the magnetic particles for charging is loaded as magnetic particles for a charging member. Next, a metal drum having the same dimensions as the photoreceptor to be used is loaded, a DC bias having the same polarity as the toner charging polarity is applied to the charging portion, and the photoreceptor is driven under the conditions for charging. The charge amount of the transferred toner is measured.

In the electrophotographic apparatus of the present invention, a magnetic brush is used as a charging member that comes into contact with the photoreceptor. The structure is such that a magnet roll or a magnet roll is provided inside as the resin-coated magnetic particle holding member. A conductive sleeve whose surface is uniformly coated with magnetic particles is preferably used.

The closest gap between the charging magnetic particle holding member and the photosensitive member is preferably 0.3 mm to 2.0 mm. When it is closer than 0.3 mm, depending on the applied voltage,
Leakage may occur between the conductive portion of the magnetic particle holding member for charging and the photoconductor, which may damage the photoconductor.

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 photosensitive member, but moves in the opposite direction from the viewpoint of the ability to take in the residual toner after transfer. Is preferred.

The amount of the charging magnetic particles held by the charging magnetic particle holding member is preferably from 50 to 500 mg /
cm ² , and more preferably 100 to 300 mg / cm ² , can provide stable chargeability.

Further, extra charging magnetic particles may be held in the charger and circulated. As image exposure means,
Known means such as a laser and an LED can be used.

In the present image forming method, a preferable step in the cleanerless image forming method can be added. After the transfer step in the image forming method of the present invention,
And by having a photoconductor potential control member before the charging step,
The stability is further improved as an image forming method.

As the photosensitive member potential control member, a member that emits light to control the photosensitive member potential, or a conductive roller, blade, or fur brush arranged in contact or close proximity is used. Among them, a roller and a fur brush are particularly preferably used. When a voltage is applied to these to control the potential of the photoconductor, it is preferable to control the polarity to the opposite of that of the charging process of the photoconductor. The reason is that the photoconductor potential is adjusted to a lower side before the photoconductor charging step, and the history of the preformed image is erased to assist the charging uniformity.

Further, the preferable resistance value of the photosensitive member potential control member is determined in place of the photosensitive member of the device actually mounted.
Attach a metal drum made of SUS or aluminum to ground. The resistance value of the member obtained from the current flowing when 50 V is applied to the photosensitive member control member is 10 ⁴ Ωcm to ¹⁰ 10 Ωcm.
It is preferably Ωcm. If it is 10 ⁴ Ωcm or less, if a pinhole is present in the photoreceptor when a voltage is applied, a pinhole leak occurs to disturb the image. Further 10 ¹⁰ Ωc
m or more, the surface potential of the photoreceptor cannot be sufficiently controlled.

The developing means is not particularly limited, but in the case of an image forming apparatus having no cleaning means, reversal development is preferable, and a structure in which the developer and the photoreceptor are in contact 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 and the transfer residual toner are in contact with each other on the photoreceptor, a rubbing force is applied to the electrostatic force, so that the transfer residual toner tends to be effectively collected by the developing unit. Regarding the bias applied to the development, it is preferable that the DC component comes between the potential of the black portion (image exposed portion) and the potential of the white portion.

Further, as a transfer means, a known method such as a corona, a roller, or a belt is used.

Further, when the transfer residual toner is collected, and is conveyed to the developing portion by utilizing the surface of the photoreceptor by using the surface of the photoreceptor and is collected and reused, it can be realized without changing the charging bias of the photoreceptor. However, in practice, when a transfer paper jam occurs or when images with a high image ratio are continuously taken, it is conceivable that the toner may be mixed into an excessive amount of the toner charger.

In this case, during the image forming operation, it is possible to move the toner from the charger to the developing machine by utilizing a portion where no image is formed on the photosensitive member. The image forming portion is, for example, during pre-rotation, post-rotation, and between transfer sheets.
In that case, it is also preferable to change the charging bias so that the toner is more easily transferred to the photoconductor than the charger.
As the bias that is likely to come out of the charger, the AC component is set to a smaller peak-to-peak voltage or a DC component.
Alternatively, there is a method in which the peak-to-peak voltage is made the same and the waveform is changed to reduce the AC effective value.

Further, in consideration of the service life of the charger portion and the use of the non-magnetic sleeve enclosing the magnet by utilizing the present image forming method, the configuration is such that toner can be further added due to cost requirements. Is preferred. In this 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, a magnetic pole structure capable of mechanically stirring or circulating magnetic particles,
Alternatively, it is preferable to provide a member for moving the magnetic particles in a container storing the magnetic particles. For example,
Behind the magnetic brush, there may be mentioned a screw member for stirring, a configuration in which a repulsion pole is provided and recoating is performed while peeling off the magnetic particles, and an obstruction member which obstructs the flow of the magnetic particles is provided.

Further, a process cartridge based on the present image forming method can be prepared.

[0159]

The present invention will be described below with reference to examples.
This does not limit the present invention.

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

[Production Example 1 of Charging Magnetic Particles] Fe ₂ O ₃ 53 mol% CuO 23 mol% ZnO 24 mol% 0.05 parts by mass of phosphorus was added to the above, pulverized and mixed by a ball mill, and the dispersant and After adding a binder and water to form a slurry, a granulation operation was performed using a spray dryer.
After classification as appropriate, baking was performed at 1150 ° C. in the air.

The obtained ferrite was subjected to crushing treatment and then classified to obtain ferrite particles having an average diameter of 53 μm.

Volume resistance of ferrite particles 1 × 10 ⁷ Ωc
m. Details of the characteristics are as shown in Table 2.
Also, the shape is very good spherical.

[Production Example 2 of Magnetic Particles for Charging] 54 mol% of Fe ₂ O ₃ 31 mol% of MnO 15 mol% of MgO 15 mg or more were pulverized and mixed by a ball mill, and a dispersant, a binder and water were added to form a slurry. The granulation operation was performed using a spray dryer. After being appropriately classified, it was baked at 1200 ° C. in an atmosphere in which the oxygen concentration was adjusted, and crushed and classified to obtain ferrite particles having an average diameter of 41 μm and a volume resistance of 3 × 10 ⁷ Ωcm. The shape is very good spherical.

Table 2 summarizes the characteristics.

[Example 3 of Production of Magnetic Particles for Charging] Same as Example 1 of production of magnetic particles for charging, except that after the granulation operation using a spray drier, the classification conditions were changed and fine granules were collected. To produce ferrite particles.

Table 2 summarizes the characteristics.

[Charging Magnetic Particle Production Example 4] Same as Charging Magnetic Particle Production Example 1 except that after the granulation operation using a spray drier, the classification conditions were changed and fine granules were collected. To produce ferrite particles.

Table 2 summarizes the characteristics.

[Example 5 of Production of Magnetic Particles for Charging] Same as Example 2 of production of magnetic particles for charging, except that after the granulation operation using a spray drier, the classification conditions were changed and fine granules were collected. To produce ferrite particles.

Table 2 summarizes the characteristics.

[Charging Magnetic Particle Production Example 6] The magnetic particles of Charging Magnetic Particle Production Example 2 and the magnetic particles of Charging Magnetic Particle Production Example 5 were mixed at a ratio of 1: 1.

Table 2 summarizes the characteristics.

[Production Example 7 of Magnetic Particles for Charging] The magnetic particles of Production Example 2 for magnetic particles for charging were pulverized by a ball mill, and then fine powder was cut by an air classifier.

Table 2 summarizes the characteristics.

[Charging Magnetic Particle Production Example 8] The magnetic particles of Charging Magnetic Particle Production Example 1 and the magnetic particles of Charging Magnetic Particle Production Example 4 were mixed at a ratio of 1: 1.

Table 2 summarizes the characteristics.

[Production Example 9 of Magnetic Particles for Charging] The magnetic particles of Production Example 1 for magnetic particles for charging were pulverized by a ball mill, and then fine powder was cut by an air classifier.

Table 2 summarizes the characteristics.

[Production Example 10 of Magnetic Particles for Charging] After the magnetic particles of Production Example 3 for magnetic particles for charging were pulverized with a ball mill,
Fine powder was cut by an air classifier.

Table 2 summarizes the characteristics.

[Production Example 11 of Magnetic Particles for Charging] Fe ₂ O ₃ 53 mol% CuO 23 mol% ZnO 24 mol% The above components were pulverized and mixed by a ball mill, and a dispersant, a binder and water were added to form a slurry. The granulation operation was performed using a spray dryer. After classification as appropriate, in air, 11
The firing was performed at 50 ° C.

After the obtained ferrite was crushed and classified, ferrite particles having an average diameter of 43 μm were obtained.

Volume resistance of ferrite particles 1 × 10 ⁸ Ωc
m. Details of the characteristics are as shown in Table 2.
Also, the shape is very good spherical.

[Example 12 of Production of Magnetic Particles for Charging] Same as Example 11 of production of magnetic particles for charging, except that after the granulation operation using a spray drier, the classification conditions were changed and fine granules were collected. To produce ferrite particles.

Table 2 summarizes the characteristics.

[Charging Magnetic Particle Production Example 13] The magnetic particles of Charging Magnetic Particle Production Example 11 and Charging Magnetic Particle Production Example 12
Were mixed at a ratio of 1: 1.

Table 2 summarizes the characteristics.

[Production Example 14 of Magnetic Particles for Charging] The magnetic particles of Production Example 11 for magnetic particles for charging were pulverized by a ball mill, and then fine powder was cut by an air classifier.

Table 2 summarizes the characteristics.

[Production Example 15 of Magnetic Particles for Charging] Fe ₂ O ₃ 53 mol% MnO 23 mol% ZnO 24 mol% The above components were pulverized and mixed by a ball mill, and a dispersant, a binder and water were added to form a slurry. The granulation operation was performed using a spray dryer. After appropriate classification, baking was performed at 1200 ° C. in a nitrogen atmosphere.

The obtained ferrite was subjected to crushing treatment and then classified to obtain ferrite particles having an average diameter of 43 μm.

Volume resistance of ferrite particles 2 × 10 ⁶ Ωc
m. Details of the characteristics are as shown in Table 2.
Also, the shape is very good spherical.

[Charging Magnetic Particle Production Example 16] The same as Charging Magnetic Particle Production Example 15 except that after the granulation operation using a spray drier, the classification conditions were changed and fine granules were collected. To produce ferrite particles.

Table 2 summarizes the characteristics.

[Production Example 17 of Magnetic Particles for Charging] The magnetic particles of Production Example 15 for magnetic particles for charging and Production Example 16 of Magnetic Particles for Charging
Were mixed at a ratio of 1: 1.

Table 2 summarizes the characteristics.

[Production Example 18 of Magnetic Particles for Charging] The magnetic particles of Production Example 15 for magnetic particles for charging were pulverized by a ball mill, and then fine powder was cut by an air classifier.

Table 2 summarizes the characteristics.

[Charging Magnetic Particle Production Example 19] The magnetic particles of Charging Magnetic Particle Production Example 3 and the magnetic particles of Charging Magnetic Particle Production Example 7 were mixed at a ratio of 9: 1.

Table 2 summarizes the characteristics.

[Charging Magnetic Particle Production Example 20] The magnetic particles of Charging Magnetic Particle Production Example 3 and the magnetic particles of Charging Magnetic Particle Production Example 7 were mixed at a ratio of 8: 2.

Table 2 summarizes the characteristics.

[Charging Magnetic Particle Production Example 21] The magnetic particles of Charging Magnetic Particle Production Example 3 and the magnetic particles of Charging Magnetic Particle Production Example 7 were mixed at a ratio of 5: 5.

Table 2 summarizes the characteristics.

[Charging Magnetic Particle Production Example 22] The magnetic particles of Charging Magnetic Particle Production Example 3 were pulverized with a ball mill.
Fine powder was cut by an air classifier.

Table 2 summarizes the characteristics.

[Production Example 23 of Magnetic Particles for Charging] Average diameter 11
The surface is oxidized to a spherical iron powder of μm, and 1 × 1
Magnetic particles having a resistance of 0 ² Ωcm were obtained.

[Production Example 24 of Magnetic Particles for Charging] Magnetism for Charging
The magnetic particles of Particle Production Example 5 were kept at 600 ° C. in a nitrogen atmosphere.
C 1 × 10 ^FourMagnetic particles having a resistance of Ωcm were obtained.

[Charging Magnetic Particle Production Example 25] The magnetic particles of Charging Magnetic Particle Production Example 3 and the magnetic particles of Charging Magnetic Particle Production Example 23 were mixed at a ratio of 9: 1.

Table 2 summarizes the characteristics.

[Charging Magnetic Particle Production Example 26] The magnetic particles of Charging Magnetic Particle Production Example 3 and the magnetic particles of Charging Magnetic Particle Production Example 24 were mixed at a ratio of 8: 2.

Table 2 summarizes the characteristics.

[Example 27 of Preparation of Magnetic Particles for Charging] The magnetic particles 100 prepared in Production Example 7 of Magnetic Particles for Charging were dissolved in a solution of 0.03 parts by mass of a silane coupling agent, dodecyltrimethoxysilane and 20 parts by mass of methyl ethyl ketone.
The mass part was added, the temperature was kept at 70 ° C. with stirring, and after the solvent was evaporated, it was placed in an oven at 150 ° C. and cured. The characteristics are summarized in Table 2.

[Production Example 28 of Magnetic Particles for Charging] 100% by weight of the magnetic particles produced in Production Example 7 of magnetic particles for charging in a solution dissolved in 0.03 parts by mass of silane coupling agent, octyltrimethoxysilane and 20 parts by mass of methyl ethyl ketone. In addition, the mixture was kept at 70 ° C. while stirring, and after evaporating the solvent, it was placed in an oven at 100 ° C. for curing. The characteristics are summarized in Table 2.

[Production Example 29 of Magnetic Particles for Charging] Magnetic particles produced in Production Example 7 of Magnetic Particles for Charging in a solution dissolved in 0.03 parts by mass of titanium coupling agent, isopropoxytriisostearoyl titanate and 20 parts by mass of toluene. After adding 100 parts by mass and keeping the temperature at 70 ° C. with stirring, and evaporating the solvent, the solution was placed in an oven at 200 ° C. and cured. The characteristics are summarized in Table 2.

[Photoconductor Production Example 1] Four functional layers are provided on an aluminum cylinder having a diameter of 30 mm.

The first layer is an undercoating 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 the reflection of laser exposure.

The second layer is a positive charge injection preventing layer, which serves to prevent the positive charge injected from the aluminum substrate from canceling the negative charge charged on the surface of the photoreceptor, and comprises an amylan resin and methoxymethylated nylon. Is a medium resistance layer having a thickness of about 1 μm, the resistance of which is adjusted to about 106 Ωcm.

The third layer is a charge generation layer and has a thickness of about 0.3 μm in which a titanyl phthalocyanine pigment is dispersed in a resin.
And a positive / negative charge pair is generated by receiving 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 surface of the photoreceptor cannot move through this layer, and only the positive charges generated in the charge generation layer can be transported to the surface of the photoreceptor. The thickness was 17 μm.

The surface resistance of the photoreceptor was 3 × 10 ¹⁵ Ωcm in the case of the charge transport layer alone. A charge injection layer is 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 particles having a particle diameter of about 0.03 μm and having a reduced resistance are dispersed in 150 parts by mass with respect to 100 parts by mass of the resin, and 20 parts by mass of tetrafluoroethylene resin particles are dispersed. 1.2 parts by mass of the agent.

As a result, the surface resistance of the photosensitive member was 2 × 1
0 ¹³ Ωcm.

[Photoconductor Production Example 2] Five functional layers are provided on an aluminum cylinder having a diameter of 30 mm.

The first layer, the second layer, the third layer, and the fourth layer are formed in the same manner as in the photoreceptor manufacturing example 1, and the charge injection layer is formed on the fifth layer. The charge injection layer is made of a photocurable acrylic resin made of Sn.
The O ₂ ultrafine particles is obtained by dispersion. Specifically, antimony is doped to reduce the resistance to a particle size of about 0.03 μm.
170 parts by mass of SnO ₂ with respect to 100 parts by mass of resin, and 20 parts by mass of tetrafluoroethylene resin particles,
1.2 parts by mass of a dispersant was dispersed.

As a result, the surface resistance of the photosensitive member was 4 × 1
0 ¹² Ωcm.

[Photoconductor Production Example 3] The fifth example of Photoconductor Production Example 1
The layer was doped with antimony to reduce the resistance to a grain size of about 0.1.
A photoconductor was prepared in the same manner as in Photoreceptor Production Example 1, except that SnO ₂ particles having a particle size of 03 μm were dispersed in a photocurable acrylic resin at 200% by weight. The resistance of the photoconductor surface is 4 ×
107 Ωcm.

[Developer Production Example 1] Polyester resin 100 parts by mass Metal-containing azo dye 2 parts by mass Low molecular weight polypropylene 3 parts by mass Carbon black 5 parts by mass After the above materials were dry-mixed, biaxial kneading and extrusion set at 150 ° C. Kneaded with a machine. The obtained kneaded material was cooled, finely pulverized by an air-flow type pulverizer, and then subjected to air classification to obtain a toner composition having an adjusted particle size distribution. In this toner composition,
Externally adding 1.5 wt% of hydrophobically treated titanium oxide,
A toner having a weight average particle size of 7.0 μm was prepared.

Also, a nickel zinc ferrite having an average diameter of 50 μm coated with a silicone resin was added to 100%
6 parts by mass of the toner was mixed with the parts by mass to obtain a developer.

[Developer Production Example 2] The toner composition obtained in Developer Production Example 1 was subjected to surface treatment in a hybridization system manufactured by Nara Machinery Co., Ltd., and the ratio of toner short axis / major axis length was 0.81. Was obtained. Hereinafter, a developer was prepared in the same manner as in Developer Production Example 1.

[Developer Production Example 3] The toner composition obtained in Developer Production Example 1 was subjected to a surface treatment in a hybridization system manufactured by Nara Machinery Co., Ltd., and the ratio of toner short axis / major axis length was 0.88. Was obtained. Hereinafter, a developer was prepared in the same manner as in Developer Production Example 1.

[Developer Production Example 4] The toner composition obtained in Developer Production Example 1 was treated in a warm bath at 60 ° C., dried, and classified to obtain a toner composition of 0.92. . Hereinafter, a developer was prepared in the same manner as in Developer Production Example 1.

[Developer Production Example 5] 88 parts by mass of styrene
12 parts by mass of n-butyl acrylate, 0.2 parts by mass of divinylbenzene, 3 parts by mass of low molecular weight polypropylene, 4 parts by mass of carbon black, 1.2 parts by mass of metal-containing azo dye,
3 parts by mass of an azo-based initiator are dispersed and mixed, and the above solution is added to 500 parts by mass of pure water in which 4 parts by mass of calcium phosphate is dispersed, and the mixture is dispersed with a homomixer. After filtering and washing, dry classification is performed,
A toner composition was obtained.

To the above toner composition, 1.5 wt% of hydrophobically treated titanium oxide was externally added, and the weight average diameter was 6.3 μm.
Was created.

The obtained toner is formed by a polymerization method, and when observed with an electron microscope, shows a true spherical shape. The ratio of the minor axis / major axis length is 0.97.

A nickel-zinc ferrite having an average diameter of 50 μm coated with a silicone resin was added to 100%
6 parts by mass of the toner was mixed with the parts by mass to obtain a developer.

Next, the present invention will be described using evaluation machines and methods used in Examples and Comparative Examples of the present invention, and Examples and Comparative Examples.

[Digital Copier 1] A digital copier using a laser beam as an electrophotographic apparatus (manufactured by Canon:
GP55) was prepared. An outline of the device is provided with a corona charger as a charging unit of the photoreceptor, and a one-component developing device employing a one-component jumping developing method as a developing unit.
A transfer unit includes a corona charger, a blade cleaning unit, and a pre-charging exposure unit. The photosensitive member charger, the cleaning means, and the photosensitive member are an integrated unit. The process speed is 150 mm / s. The digital copier was modified as follows.

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

The development part was changed from one-component jumping development to
Modifications were made so that a two-component developer could be used. Further, a 16Φ conductive non-magnetic sleeve containing a magnet roller is arranged on the charged portion to form a charging magnetic brush. Further, the transfer means using a corona charger was changed to a roller transfer method, and the pre-charge exposure means was removed.

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

The developing bias superimposes a rectangular wave of 1000 Vpp / 3 kHz on a DC component of -500 V.

Further, remove the cleaning blade,
It was a cleanerless copying machine. FIG. 5 is a schematic diagram. In FIG. 5, reference numeral 501 denotes an image fixing device;
03 is a magnetic particle for charging, 504 is a conductive sleeve, 50
5 is a photoconductor, 506 is an image exposure, 507 is a developing sleeve,
508 is a developing device, 509 and 510 are stirring screws, 5
11 is a developer, 512 is a paper transport guide, 513 is a transfer paper, 514 is a transfer roller, and 515 is a paper transport belt.

(Embodiment 1) Using a digital copying machine 1,
180mg / cm coating density of magnetic particles ^TwoTona
And a photoreceptor.

In order to mount it at 180 mg / cm ² , a minimum amount of about 30 g is required.

The magnetic brush charger is rotated in the same direction at the contact portion with the photosensitive member. At this time, the rotational speed of the charger is set to 300 mm / s, and the toner passing phenomenon without the cleaner is evaluated using the image shown in FIG. The evaluation method is based on the difference between the fog appearing in the image corresponding to the second round of the photoconductor and the fog appearing in the portion not corresponding to the image in the first round of the photoconductor and the image not corresponding to the image in the first round of the photoconductor. By evaluating the absolute value of fog on the part.

In the evaluation mode, first, the bias applied to the charging member is a DC voltage of -700 V and 1 kV.
Hz, a rectangular wave AC component of 700 Vpp
/ Under the condition of 60% relative humidity, the developing bias is −50.
A rectangular wave of 1000 Vpp / 3 kHz is superimposed on the DC component of 0 V, the image of FIG. 6 is copied, and the initial slip-through phenomenon is evaluated. The image is evaluated at a peripheral speed of the charger of 300 mm / s.

As the rotational peripheral speed is higher, the effect of scraping off the transfer residual toner is greater, and the effect of preventing the slip-through phenomenon is higher.

Next, 20 cycles, that is, 1000 copies of the solid black 20% band image as shown in FIG. 6 in a 50-sheet intermittent mode under the condition of a rotational peripheral speed of 300 mm / s, are evaluated in the same manner as in the initial stage. At this time, for the non-image forming unit,
At the time of continuous paper feeding, at the time of charging (at the time of pre-rotation), before image formation (between papers), and 5
At the time of photoconductor charging after completion of image formation on the 00th sheet (post-rotation)
About -700 V DC voltage and 1 kHz, 3
A rectangular wave AC component of 00 Vpp is applied to charge the photoconductor, and the toner mixed in the charged magnetic brush is moved onto the photoconductor and collected at the developing portion.

The fog is a reflection type densitometer (TOKYO DE)
NSHOKU CO. , LTD REFLECTOM
(ETER ODEL TC-6DS) was used (Ds is the worst value of the reflection density of the white background after printing, and Ds-Dr is the fogging amount when the average reflection density of the paper before printing is Dr). (A fogging amount of 2% or less is a good image having substantially no fogging, and a fogging amount of more than 5% is an unclear image in which fogging is conspicuous.)
If it is 2.0% or more, it is a level at which the slip-through portion appears to be emphasized.

The above evaluation is performed using the magnetic particles of Production Example 7 of the magnetic particles, the developer of Production Example 5 of the developer, and the photoreceptor of Production Example 1 of the photoreceptor. As a result, the image was substantially free from fogging at a peripheral speed of the charger of 300 mm / s, and good results were obtained.

Table 3 summarizes the results. In addition, when the frictional charging properties of the magnetic particles of Magnetic Particle Production Example 7 and the toner used in Developer Production Example 5 were confirmed, it was negative, which is the same polarity as the charging polarity of the photoconductor of this example.

(Examples 2 to 15) Evaluations similar to those in Example 1 were made using combinations shown in Table 3. Table 3 summarizes the results.

When the triboelectric charging properties of the magnetic particles used in Examples 2 to 15 and the toner used in Developer Production Example 5 were confirmed, the charging polarity was the same as that of the photoreceptor of this example. The polarity was negative.

From the results of the above examples, in Examples 2 to 5 and Examples 12 to 15, very good results were obtained with almost no fogging due to slip-through. This is because the ratio of the minor axis length / major axis length of the 5 μm to 20 μm portion of the used magnetic particles is 0.80 or less and smaller than the ratio of the minor axis length / major axis length of the toner. The effect is as follows.

In Examples 6 to 8, when the ratio of the minor axis length / major axis length of the magnetic particles used was 0.85, the level of the slip-through portion was not so high as to be seen. Fog due to slip-through tends to appear relatively easily, and the ratio of the minor axis length / major axis length of the toner is 0.85.
Beyond the level will improve.

Further, in Examples 9 to 11,
When the short axis length / long axis length of the magnetic particles used is 0.80, the level of the short axis of the magnetic particles is not as high as that of Example 9, although the level of the slip-through portion is not emphasized. When the major axis length is larger than the ratio of the minor axis length / major axis length of the toner, fog tends to appear.

(Comparative Examples 1 to 7) The combinations shown in Table 3 were evaluated in the same manner as in the examples. Table 3 summarizes the results.

From the results of the above Comparative Examples, in Comparative Examples 1 to 4, fog was at a level without any problem, but the ratio of the minor axis length / major axis length of the magnetic particles used was It is 0.85 or more, which is a level at which fog is increased due to slippage at 1000 sheets due to insufficient toner scraping effect, and the slipped-through portion is emphasized.

In Comparative Example 5, the average particle size of the magnetic particles was too small, and the amount of the particles having a particle size of 2 μm or less was as large as 11.05% by volume. Since it appeared, the evaluation was discontinued.

In Comparative Examples 6 and 7, the level was not problematic at the beginning, but at 1000 sheets, the ratio of the minor axis length / major axis length of the particles used was 0.85 or more. 1000 due to insufficient toner scraping effect
At the time of printing, an increase in fog due to slip-through is recognized, and the slip-through portion is emphasized. In addition, 10
The fog at the time of 00 sheets increased, and the image became conspicuous, and a leak image partially resulted from the reduction in resistance.

(Example 16) [Evaluation method] The magnetic particles of Production Example 27 of the magnetic particles, the developer of Production Example 5 of the developer, and the photoreceptor of Production Example 1 of the photoreceptor were subjected to Coating density is 1
It is mounted on a charger so as to be 80 mg / cm ^2, and a photoreceptor is mounted.

In order to mount the cartridge at 180 mg / cm ² , a minimum amount of about 30 g is required. In this embodiment, 40 g was loaded. The magnetic brush charger is rotated in a reverse direction at a contact portion with the photoconductor. At this time, the rotational speed of the charger is 240 mm / s.

The evaluation mode is as follows.
1000 sheets are continuously fed in horizontal feed. At this time, as a bias applied to the charging member, a DC voltage of -700 V and a rectangular wave AC component of 1 kHz and 700 Vpp are applied, and a durability test is performed under the conditions of 25 ° C./60% relative humidity.

Further, in the non-image forming portion, during continuous paper feeding, charging (before rotation) before image formation of the first first sheet, image formation (between sheets), and 1000 minutes.
At the time of photoreceptor charging (post-rotation) after the completion of image formation on the sheet, a DC voltage of -700 V and 1 kHz, 500
A rectangular wave AC component of Vpp is applied, and while the photoconductor is charged, the toner mixed in the charged magnetic brush is moved onto the photoconductor and collected at the developing portion.

In the present embodiment, the timing for applying the charging bias different from that for charging the photoreceptor is selected at the time of pre-rotation, at the time of post-rotation, and between sheets. However, the present invention is not limited to this. The timing at which the photoconductor moves may be measured.

At this time, as shown in FIG. 1, the toner remaining after transfer is collected by a magnetic brush, its frictional charging polarity is made the same as that of the photoreceptor, and part of the toner is developed or collected over the photoreceptor. .

The applied voltage is -7 for every 20,000 sheets of durability.
A DC voltage of 00 V and a rectangular AC component of 1 kHz and 700 Vpp were applied, and the convergence rate was measured as to what percentage of the DC component -700 V of the charging potential of the photoconductor surface from 0 V reached.

The convergence rate is good if it is 90% or more.
% Or more, excellent chargeability is obtained.

Further, using the image as shown in FIG. 6, the toner slip-through phenomenon without the cleaner is evaluated.
The evaluation method is based on evaluating fog in the second rotation of the photoconductor that appears in a portion corresponding to the image in the first rotation of the photoconductor.

The fog was measured using a reflection densitometer (TOKYO DEN).
SHOKU CO. , LTD REFLECTOME
TER ODEL TC-6DS) (Ds is the worst value of the reflection density of the white background after printing, and Ds-Dr is the fogging amount when the average reflection density of the paper before printing is Dr). (A fogging amount of 2% or less is a good image having substantially no fogging, and a fogging amount of more than 5% is an unclear image with noticeable fogging.) As a result, as shown in Table 4, even at 60,000 sheets An image having excellent fog resistance and no fog and without emphasizing fog due to slippage was obtained.
No charging failure occurred due to the scraping of the photoreceptor.

When the frictional charging properties of the magnetic particles of Production Example 27 of the magnetic particles used in this example and the toner used in Production Example 5 of the developer were confirmed, the same polarity as the charging polarity of the photoreceptor of this example was confirmed. Was a minus.

Example 17 The same evaluation as in Example 16 was carried out, except that the magnetic particles of Production Example 28 were used, and good results were obtained. Table 4 shows the results. When the frictional charging properties of the magnetic particles of Production Example 27 of the magnetic particles used in the present example and the toner were confirmed, it was negative, which is the same polarity as the charging polarity of the photoreceptor of the present example.

Example 18 The same evaluation as in Example 16 was carried out except that the magnetic particles of Production Example 29 were used, and good results were obtained. Table 4 shows the results. When the frictional charging properties of the magnetic particles and the toner of Production Example 29 of the magnetic particles used in the present example were confirmed, the negative polarity was the same as the charging polarity of the photoconductor of the present example.

Example 19 The same evaluation as in Example 16 was carried out except that the magnetic particles of Production Example 7 were used, and good results were obtained. Table 4 shows the results. However, the photoconductor was replaced with a new one at the time of 50,000 sheets due to the photoconductor scraping. When the frictional charging properties of the magnetic particles of the magnetic particle production example 7 used in the present example and the toner were confirmed, the negative polarity was the same as the charging polarity of the photoreceptor of the present example.

(Example 20) In Example 16, an electrophotographic digital copying machine provided with a bar-type fur brush 716 as shown in FIG. 7 before charging and after the transfer step was used. 7, parts equivalent to those shown in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted.

A DC voltage of +400 V was applied during the operation of the machine, and the same evaluation as in Example 16 was performed. As a result, as shown in Table 4, even at 60,000 sheets, an image having excellent fog resistance was obtained, and no fog was observed and fog was not emphasized due to slip-through.

There was no occurrence of charging failure due to scraping of the photoreceptor.

(Comparative Example 8) The same evaluation as in Example 16 was performed except that the magnetic particles of Production Example 3 were used. As shown in Table 4, up to 20,000 sheets, the fog due to slip-through was slightly emphasized, but there was no problem with charging potential convergence and fog. Deterioration and fog increased.

(Comparative Example 9) The same evaluation as in Example 16 was performed, except that the magnetic particles of Production Example 6 were used. As shown in Table 4, up to 40,000 sheets, the image was slightly enhanced with fog due to slip-through, but no problem was observed with respect to the charge potential convergence and fog. Slightly deteriorated. However, the photoreceptor was replaced with a new one after 50,000 sheets due to the photoreceptor scraping.

Comparative Example 10 The same evaluation as in Example 16 was performed, except that the magnetic particles of Production Example 3 and the photoreceptor of Production Example 3 were used. From the beginning, the image had a slight blur, and as shown in Table 4, up to 20,000 sheets, the image was slightly enhanced with fog due to slip-through. However, at the time of 40,000 sheets, deterioration of potential convergence and fog increased.

[0282]

[Table 1]

[0283]

[Table 2]

[0284]

[Table 3]

[0285]

[Table 4]

[0286]

[Table 5]

[0287]

As described above, the present invention provides a photosensitive member having a photosensitive layer on a conductive support and having a charge injection layer furthest from the conductive support layer and comprising magnetic particles. Contacting a charging member and applying a voltage to charge the photoreceptor, exposing the photoreceptor to form a latent image, and visualizing the latent image with toner; The voltage applied to the member is a DC voltage in which a vibration voltage of 1000 V or less is superimposed between peaks, the average diameter of the magnetic particles is 10 μm or more and 40 μm or less, and the short length of the particles of 5 μm to 20 μm of the magnetic particles is reduced. The ratio of the shaft length / major axis length is 0.85 or less, and the volume resistivity of the entire magnetic particle is 10 ⁴ to 10 ⁹ Ωcm. As a result, a highly durable charging member can be realized, and an image forming method with stable charging properties can be obtained for a long period of time, particularly in a cleanerless system.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating the principle of an image forming method according to the present invention.

FIG. 2 illustrates a case where a toner obtained by kneading and pulverizing a resin and a colored powder is used as a charging member using particles having a shape close to a true sphere.
FIG. 4 is an explanatory diagram illustrating the behavior of transfer residual toner on the surface of a photoconductor.

FIG. 3 is an explanatory diagram showing the behavior of the transfer residual toner on the surface of the photoconductor in the case where particles having irregular shapes are used and the toner has a shape close to a true sphere as a toner.

FIG. 4 is an explanatory view showing a method of measuring the volume resistance of magnetic particles.

FIG. 5 is an explanatory diagram showing a configuration of an electrophotographic digital copying machine.

FIG. 6 is a plan view of an image used for evaluation.

FIG. 7 is an explanatory diagram showing a configuration of a digital copying machine in which a fur brush is added to the digital copying machine of FIG. 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Developer 11 Magnetic brush charger 12 Photoreceptor 13 Image exposure 14 Transfer roller 15 Charging magnetic particle 16 Conductive sleeve 17 Developing sleeve 18 Developing device 19 Stirring screw 21 Photoreceptor surface layer 22,23,24,25,26 Magnetism Particle 27 Transfer residual toner 31 Photoreceptor surface layer 32, 33, 34, 35 Magnetic particle 36, 37, 38 Transfer residual toner A Measurement cell 41, 42 Electrode 43 Guide ring 44 Ammeter 45 Voltmeter 46 Constant voltage device 47 Measurement sample 48 Insulator 501 Image fixing device 502 Charger 503 Charging magnetic particles 504 Conductive sleeve 505 Photoconductor 506 Image exposure 507 Developing sleeve 508 Developing device 509, 510 Stirring screw 511 Developer 512 Paper transport guide 513 Transfer paper 514 Transfer roller 515 Paper transport belt

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Fumihiro Arahira 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Tomoji Ishihara 3-30-2 Shimomaruko, Ota-ku, Tokyo Non Corporation

Claims (23)

[Claims] 1. A photosensitive member having a photosensitive layer on a conductive support and having a charge injection layer farthest from the conductive support layer,
An image forming method comprising the steps of: contacting a charging member made of magnetic particles and applying a voltage to charge a photosensitive member, exposing the photosensitive member to form a latent image, and visualizing the latent image with toner In the above, the voltage applied to the charging member is a DC voltage in which an oscillating voltage having a peak-to-peak voltage of 1000 V or less is superimposed. An image forming method, wherein the ratio of the minor axis length / major axis length of the particles is 0.85 or less, and the volume resistivity of the magnetic particles as a whole is 10 ⁴ to 10 ⁹ Ωcm. 2. When the volume resistance of the magnetic particles of 5 μm to 20 μm is Ra, and the volume resistance of the magnetic particles exceeding 20 μm is Rb, 0.5 ≦ Ra / Rb ≦ 5. The image forming method according to claim 1, wherein 0. 3. When the volume resistivity of the magnetic particles of 5 μm to 20 μm is Ra, and the volume resistivity of the magnetic particles exceeding 20 μm is Rb, 1.0 ≦ Ra / Rb ≦ 5. The image forming method according to claim 1, wherein 0. 4. The ratio of minor axis length / major axis length of a portion exceeding 20 μm of the magnetic particles is 0.85 or less.
4. The image forming method according to any one of claims 1 to 3. 5. The image forming method according to claim 1, wherein the ratio of the minor axis length / major axis length of the particles of 5 μm to 20 μm in the magnetic particles is 0.80 or less. . 6. A step of transferring a visualized toner image to a transfer member, and further comprising a step of cleaning in a developing step without an independent cleaning step of cleaning residual toner on the photosensitive member. 1 to
6. The image forming method according to any one of 5. 7. The image forming method according to claim 6, further comprising a photosensitive member potential control member after the transfer step and before the charging step. 8. The image forming method according to claim 7, wherein the photoconductor potential control member is a member to which a voltage is applied, and the photoconductor potential control member is applied with a polarity opposite to a charging polarity in the charging step. 9. The ratio A of the minor axis length / major axis length of the 5 μm to 20 μm portion of the magnetic particles, and the minor axis length / major axis length ratio B of the toner is A <B. The image forming method according to claim 1. 10. The image forming method according to claim 1, wherein the ratio B of the minor axis length / major axis length of the toner exceeds 0.8. 11. The image forming method according to claim 1, wherein the ratio B of the short axis length / long axis length of the toner exceeds 0.9. 12. The image forming method according to claim 1, wherein the heat loss of the magnetic particles is 0.5% by mass or less. 13. The surface of the magnetic particles is treated with a coupling agent whose central element having an alkyl chain of C6 or more is titanium, silicon, aluminum, or zirconium, and the amount of the coupling agent is: 0.
The image forming method according to claim 1, wherein the content is from 0001% by mass to 0.5% by mass. 14. The magnetic particles having a particle size distribution of 5 μm or less.
The image forming method according to claim 1, wherein the image forming method has two or more peaks or shoulders in a range of 60 μm. 15. The charge injection layer having a volume resistivity of 1 ×
The image forming method according to any one of claims 1 to 14, wherein the density is 10 < ⁸ > to 1 * 10 < ¹⁵ > [Omega] cm. 16. The image forming method according to claim 15, wherein said charge injection layer comprises conductive fine particles and a binder resin. 17. The image forming method according to claim 15, wherein the charge injection layer contains a lubricant powder. 18. The method according to claim 1, wherein the lubricant powder is a fluororesin, a silicone resin or a polyolefin resin.
8. The image forming method according to item 7. 19. The toner according to claim 1, wherein the frictional charging polarity of the toner is the same as the charging polarity of the photoconductor, and the developing step is a reversal development.
The image forming method according to any one of the above items. 20. The image forming method according to claim 1, wherein the magnetic particles are manufactured by pulverizing ferrite particles. 21. The volume ratio of the magnetic particles occupying 5 μm to 15 μm is not less than 10% by volume with respect to all the magnetic particles.
The image forming method according to claim 1, wherein the content is 0% by volume or less. 22. The volume ratio of the magnetic particles occupying 5 μm to 15 μm is not less than 15% by volume with respect to all the magnetic particles.
The image forming method according to claim 1, wherein the content is 0% by volume or less. 23. The image forming method according to claim 1, wherein a volume ratio of the magnetic particles occupying 2 μm or less is 5% by volume or less.