JP2001034039A - Image forming method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent fogging and toner scattering from being increased even when image forming operation is repeated over a long term while rotating a small-diameter electrification sleeve at high speed and performing electrification by making the triboelectrification amount of toner with electrically conductive magnetic particles and magnetic carrier particles satisfy specified relation. SOLUTION: The triboelectrification amount Q1 of the toner with the electrically conductive magnetic particles for electrification and the triboelectrification amount Q2 of the toner with the magnetic carrier particles for developing satisfy the relation 0<Q2<=Q1 (mC/kg) or 0>Q2>=Q1 (mC/kg). When Q1 and Q2 are equal, the triboelectrification amount distribution of the toner in a developing device is not widened even when the electrically conductive particles for electrification intrude in the developing device. Even when Q1 is larger than Q2 as an absolute value, the electrification amount distribution of the toner in the entire developing device is hardly changed from a state before the intrusion of the conductive particles for electrification if all the magnetic carrier particles for developing in a developing container are in such extend that their triboelectrification polarity is not reversed by a few conductive magnetic particles for electrification. Therefore, the fogging and the toner scattering hardly occur.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method and an image forming apparatus used for a copying machine, a printer or a facsimile, and more particularly, to developing an electrostatic latent image formed on an image carrier with toner. The present invention relates to an image forming method and an image forming apparatus using an electrophotographic method.

[0002]

2. Description of the Related Art Conventionally, a general image forming method using an electrophotographic method includes a charging step of charging an image carrier, a latent image forming step of forming an electrostatic latent image on the charged image carrier, The image forming apparatus includes a developing step of developing a latent image to form a toner image and a transfer step of transferring the toner image to a transfer material.

However, in the above-mentioned conventional image forming apparatus, since a corona charger is used as a charging device for charging a photosensitive member, ozone is generated by corona discharge during charging. .

[0004] In recent years, as environmental awareness has increased, a contact charging system has been used as a charging method that does not use corona discharge accompanied by generation of ozone. As such a charging member of the contact charging system, for example, Japanese Unexamined Patent Publication No.
A magnetic brush type charging device as described in JP-A-57958 is preferably used in view of stability of charging contact.

However, when the above-described magnetic brush type contact charging device (magnetic brush charger) is used to perform the two-component contact development as a development, and the image forming operation is repeated, fog is gradually generated in the image. There is a problem that toner scattering from the developing device also increases.

The inventors of the present invention have conducted various studies on the above-mentioned phenomena in which the fog and toner scattering increase. As a result, these phenomena were found to be reduced as the image forming operation progressed. It has been found that this is caused by gradually mixing in the developing container. Hereinafter, the mechanism by which the conductive magnetic particles for charging are mixed into the developing container, and the reason for the occurrence of fog and toner scattering will be described.

In the magnetic brush charger, conductive magnetic particles for charging are magnetically carried by a charging sleeve containing a magnet with a binding force to form a magnetic brush.
The surface of the photoconductor is charged by the magnetic brush rubbing the surface of the photoconductor by rotation of the sleeve or the magnet. In order to improve the charging property, the magnetic brush type contact charging device carries on the charging sleeve a considerably larger amount (two times or more) of magnetic particles than the amount of developer carried on the developing sleeve of the two-component system. It is being transported. For this reason, the tip of the magnetic particle layer on the charging sleeve is hardly magnetically constrained. In particular, when a small-diameter sleeve (or magnet) is used, and when rotating at a high speed, the magnetic particles at the tip of the magnetic particle layer are separated. As a result, the separated magnetic particles adhere to the photoconductor in minute amounts, and are collected and accumulated in the developing container in the developing unit as the photoconductor rotates.

In the case of an image forming apparatus in which a cleaning device is provided upstream of the magnetic brush charger in the rotation direction of the photoconductor, toner and external additives may be removed in small amounts as the durability increases. There is a case where the toner passes through the gap between the blade and the photoconductor and enters the magnetic brush charger. As a result, the resistance of the magnetic brush gradually increases, causing a difference between the applied voltage and the surface potential of the photoconductor, and the magnetic particles adhere to the photoconductor in a potential difference.

In addition, no cleaning device is provided upstream of the magnetic brush charger in the rotation direction of the photoconductor, and a small amount of transfer residual toner remaining on the photoconductor after transfer is once taken into the charging magnetic particles of the magnetic brush charger. In a system using a cleanerless process in which the toner discharged on the photoreceptor is discharged after stirring and the toner discharged on the photoreceptor is collected in a developing container, the toner is easily accumulated in the magnetic particles for charging. Such magnetic particles having a potential difference are more easily adhered.

The conductive magnetic particles for charging accumulated in the developing container in this way are mixed and stirred with the toner in the developing container and the newly supplied toner. The relationship between the amount of charge of the toner due to the friction of the toner and the amount of charge with the toner due to the friction with the magnetic carrier particles for development has not been so often considered. However, when the charge amount of the toner is smaller than the charge amount of the toner due to friction with the magnetic carrier particles during development, or when the polarity is opposite, the charge amount distribution of the toner in the developing container increases the toner having a low charge amount. Further, when the chargeability of the magnetic carrier particles for development is reduced over a long period of time, the amount of toner having a lower charge amount increases, and as a result, fog and toner scattering increase.

EP-A-0 844 536 (corresponding to US Pat. No. 5,994,019) discloses a volume resistance value of a surface layer of a latent image carrier, a volume resistance value of a charging member of a contact charging means, and an external additive of toner. By defining the relationship between the volume resistance of the magnetic carrier of the two-component developer and the volume resistance of the two-component developer, the chargeability of the latent image carrier during charging is improved, and the electrostatic latent in the development area during development is improved. It is proposed that high quality and high durability images can be formed without causing image disturbance.

However, even in the image forming method of the prior art, the developing in the case where the image forming is repeatedly performed while the surface of the image carrier is charged by rotating at a high speed by using a small-diameter sleeve as a charging sleeve of the magnetic brush charger. In order to stabilize the properties and maintain the durability of a large number of sheets, there is a point to be further improved.

[0013]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming method and an image forming apparatus which solve the above-mentioned problems.

An object of the present invention is to provide an image forming method and an image forming method in which fog and toner scatter are not increased even when long-term image formation and durability are performed while charging the surface of an image carrier by rotating at high speed using a small-diameter charging sleeve. It is to provide a forming device.

[0015]

The above object is achieved by the following constitution of the present invention.

That is, the present invention provides (A) conductive magnetic particles, a rotatable conductive magnetic particle carrier for carrying and transporting the conductive magnetic particles, and an inside of the conductive magnetic particle carrier. Using a charging device having a plurality of magnetic field generating means provided, a voltage is applied to the conductive magnetic particle carrier, and the conductive magnetic particles are brought into contact with the image carrier to form the image carrier. (B) a latent image forming step of forming an electrostatic latent image on the charged surface of the image carrier; and (C) a toner and magnetic material facing the image carrier. A developing device having a two-component developer having carrier particles, a developer carrier for supporting the two-component developer, and a plurality of magnetic field generating means provided inside the developer carrier; To form an alternating electric field at a portion where the image carrier and the developer carrier are opposed to each other. Developing a toner image by developing the electrostatic latent image with the toner of the two-component developer, wherein the triboelectric charge amount of the toner with the conductive magnetic particles ( Q1) and the triboelectric charge (Q2) of the toner with the magnetic carrier particles in the developing device have the following relationship: 0 <Q2 ≦ Q1 (mC / k
g) or an image forming method satisfying 0> Q2 ≧ Q1 (mC / kg).

The present invention also relates to (A) a latent image carrier for carrying an electrostatic latent image; (B) conductive magnetic particles, and a rotatable conductive member for carrying and carrying the conductive magnetic particles. A conductive magnetic particle carrier, and a plurality of magnetic field generating means provided inside the conductive magnetic particle carrier, applying a voltage to the conductive magnetic particle carrier, and (C) a latent image forming means for forming an electrostatic latent image on the charged surface of the image carrier; And (D) a two-component developer having a toner and a magnetic carrier, which is opposed to the image carrier, a developer carrier for supporting the two-component developer, and A plurality of magnetic field generating means provided therein, and an alternating portion is provided at an opposing portion between the image carrier and the developer carrier. A developing device for forming a field and developing the electrostatic latent image with the toner of the two-component developer to form a toner image. And the triboelectric charge (Q1) of
The frictional charge amount (Q2) of the toner with the magnetic carrier particles in the developing device is expressed by the following relationship: 0 <Q2 ≦ Q1 (mC / k
g) or an image forming apparatus satisfying 0> Q2 ≧ Q1 (mC / kg).

[0018]

DETAILED DESCRIPTION OF THE INVENTION The present inventors have conducted intensive studies on the above-mentioned problems of the prior art, and as a result, have found that a charging device using conductive magnetic particles as a contact charging member, and a two-component system having toner and magnetic carrier particles. A developing device for developing the electrostatic latent image by forming an alternating electric field in a portion facing the image carrier using a developer; Even if the fogging and toner scattering do not occur, the relationship between the frictional charge imparting property to the toner of the conductive magnetic particles for charging and the frictional charge imparting property to the toner of the magnetic carrier is a specific relationship, that is,
Amount of frictional charge between toner and conductive magnetic particles for charging (Q1)
And the frictional charge amount (Q2) of the toner with the magnetic carrier particles for development is expressed by the following relationship: 0 <Q2 ≦ Q1 (mC / kg)
Alternatively, the present inventors have found that satisfying 0> Q2 ≧ Q1 (mC / kg) can solve the above-described problems, and have reached the present invention.

The reasons for achieving the object of the present invention as described above are as follows.

As described above, as the image forming operation is repeated, a small amount of the magnetic particles for charging accumulate in the developing container. At this time, for example, when a toner for negative charging is used, a frictional charging system is used. If the above three types of materials are selected so as to satisfy the relationship of 0> Q2 ≧ Q1, the toner is normally charged by friction with the magnetic carrier particles for development with respect to the conductive particles for charging mixed in the developing device. And the frictional charge amount is equal to or more than the frictional charge amount of the toner, and the distribution of the charge amount of the toner in the entire developing device hardly changes from that before the mixing of the conductive magnetic particles for charging. It is hard to cause toner scattering.

If the amount of frictional charge (Q1) of the toner with the conductive magnetic particles for charging and the amount of frictional charge (Q2) of the toner with the magnetic carrier particles for development are the same, the conductive material for charging in the developing device is provided. When the magnetic particles are mixed, the distribution of the triboelectric charge amount of the toner in the developing device is not widened.
In absolute value, even if Q1 is larger than Q2, all the magnetic carrier particles for development in the developing container are not so small that the triboelectric charging polarity is reversed by a small amount of conductive magnetic particles for charging. In this case, the effects described above can be effectively exhibited.

According to the detailed studies by the present inventors, the goodness of the charging conductive magnetic particles mixed in the developing device is about 20% by weight or less of all the developing magnetic carrier particles in the developing device. That is, the relationship between the amount of triboelectric charge of the toner is an absolute value,
Even when Q1 is larger than Q2, the charge amount distribution of all the toners in the developing device is preferably not broadened. If the content exceeds 20% by weight, the ratio of polarity reversal of the development carrier increases, and as a result, the polarity reversal increases as a toner, and fogging easily occurs.

Further, the amount of conductive magnetic particles for charging mixed in the developing container is not more than 20% by weight, and the triboelectric charging amounts Q1 and Q2 of the toner satisfy the following relationship: 0 <Q2 <Q1 (m
C / kg) or 0>Q2> Q1 (mC / kg), the ability of the magnetic carrier particles for development to impart a triboelectric charge to the toner decreases as the magnetic carrier particles develop and become durable. However, since the conductive magnetic particles for charging have a high ability to impart frictional charging to the toner, a decrease in the average charge amount of the toner can be suppressed and the toner can be stably maintained.

Particularly preferably, the triboelectric charge amount Q1 of the toner
And Q2 preferably satisfy the above relationship, and the following relationship 5 ≦ | Q1 | ≦ 60 (mC / kg) 60 ≦ | Q2 | ≦ 60 (mC / kg).

When the relationship between the triboelectric charge amounts Q1 and Q2 of the toner is 0 <Q1, when Q1 <Q2, or 0.
When Q1> Q2 and Q1> Q2, when the conductive magnetic particles for charging of the magnetic brush charger adhere to the surface of the photoreceptor and enter from the developing unit into the developing container, Since the distribution of the amount of triboelectricity of the toner inside is widened, fogging and toner scattering easily occur.

The value of | Q1 | and | Q2 | is 5 mC / kg
If the ratio is less than the above range, the toner easily separates from the respective carriers, thereby facilitating the scattering of the toner. In the developing section, the amount of the toner whose polarity is inverted increases, so that the reversal fog also easily occurs. Also, | Q1 | and |
When the value of Q2 | exceeds 60 mC / kg, the toner adheres to the carrier with a strong electrostatic force, so that when the black portion is developed, each carrier and the adhered toner are integrated. (The black-colored portion carrier adheres) easily occurs. On the other hand, in the developing device, an increase in the charge of the development carrier tends to cause a problem that the carrier adhesion amount in the white portion increases.

The image forming method of the present invention is embodied, for example, in the image forming apparatus shown in FIG.

FIG. 1 is a diagram showing an example of the configuration of an image forming apparatus according to the present invention.

As shown in FIG. 1, the image forming apparatus reads a document table 10 on which a document G is set, and reads an image of the document G set on the document table 10 by moving along the document table 10. A document scanning unit 9 that converts the image signal into an image signal and outputs the image signal, and rotates at a predetermined peripheral speed around a center support shaft,
Photoreceptor 1 on which image formation is performed on the surface during the rotation process
A magnetic brush charger 3 for charging the surface of the photoconductor 1 to a uniform potential; and irradiating a laser beam based on an image signal output from the original scanning unit 9 to electrostatically charge the surface of the photoconductor 1. Exposure means 11 for forming a latent image, a developing device 4b for containing toner and developing the toner on an electrostatic latent image formed on the surface of photoconductor 1 to form a toner image, and a surface of photoconductor 1 Transfer charger 7 for electrostatically transferring the toner image formed on the transfer material P onto the transfer material P, a separation charger 8 for electrostatically separating the transfer material P from the photoreceptor 1, and transfer onto the transfer material P A fixing device 6 for fixing the formed toner image onto the transfer material P by heating, and a cleaner 5 for removing extraneous matter such as residual toner remaining on the photoconductor 1 after passing through the transfer charger 7.
And a static eliminator 2 for eliminating the residual potential on the surface of the photoconductor 1 after passing through the transfer charger 7.

The original scanning unit 9 connects the original irradiating lamp that scans the original G while irradiating the original G with light, and the reflected light reflected by the original G among the irradiation light emitted from the original irradiating lamp. A short focus lens array that forms an image and outputs it as an optical signal, and a CCD sensor that converts an optical signal output from the short focus lens array into an image signal and outputs the image signal are integrally formed.

Further, the CCD sensor includes a light receiving section for converting an optical signal output from the short focus lens array provided in the original scanning unit 9 into a charge signal and outputting the charge signal, and a charge signal output from the light receiving section. And a transfer unit for transferring the charge signal transferred from the transfer unit into a voltage signal, further amplifying the voltage signal with a predetermined gain, reducing the impedance, and outputting the voltage signal. .

The operation of the image forming apparatus configured as described above will be described below.

First, the document G is set on the document table 10 with the surface to be copied facing downward, and copying is started by pressing a copy button (not shown).

Next, in the document scanning unit 9, the document irradiating lamp, the short focus lens array, and the CCD sensor are integrally scanned while irradiating the document with light. The light reflected by the G is formed into an image by the short focus lens array and is incident on the CCD sensor.

Next, in the CCD sensor, the reflected light incident on the light receiving section provided therein is converted into a charge signal, and the transfer signal is transferred to the output section in synchronization with the clock pulse in the transfer section. In the output unit, the charge signal synchronized with the clock pulse is converted into an analog signal, amplified with a constant gain, output with reduced impedance.

The analog signal output from the original scanning unit 9 is converted into a digital signal by well-known image processing in an image processing means (not shown).
Is input to

Subsequently, in the course of one rotation of the photoconductor 1, an image is formed on the surface of the photoconductor 1 based on the image signal converted into a digital signal by the image processing means.

First, the surface potential of the photoreceptor 1 is uniformly reduced by a voltage applied to the charger 3 from a power supply (not shown).
A charging process is performed so that the voltage becomes 650 V (charging step).

Next, based on the image signal input to the exposure means 11,
Scanning is performed by laser light emitted from a solid-state laser element (not shown) that is N / OFF controlled. Here, the surface potential of the portion (image portion) irradiated with the laser light is:
The voltage is attenuated to about -200 V, whereby an electrostatic latent image is formed based on the image signal (latent image forming step).

Next, in the developing device 4b, a DC voltage of -500V is applied to the developing sleeve 21 from a power supply (not shown), and a rectangular wave of Vpp (peak-to-peak voltage) = 2000V and frequency = 2000Hz is applied to the developing sleeve 21. By applying the superimposed voltage, a voltage of about 300 V between the surface potential of the image portion and the DC voltage applied to the developing sleeve 21.
A potential difference of V occurs.

Here, the toner in the developing device 4b is charged to a negative (negative) polarity and is conveyed onto the developing sleeve 21, and is carried on the developing sleeve 21 by a magnetic force. The toner carried on the sleeve 21 electrostatically adheres to the surface of the photoreceptor 1 by the contrast potential, which is the above-mentioned potential difference, so that the electrostatic latent image formed on the surface of the photoreceptor 1 is visualized by the toner. Thus, a toner image is formed (development step).

Incidentally, the above-mentioned developing method is, in particular,
This is called a reversal development method.

Next, the toner image formed on the surface of the photoreceptor 1 receives a constant electric field by a voltage applied to the transfer charger 7 from a power supply (not shown), and is electrostatically placed on the transfer material P. Batch transfer (transfer step).

Thereafter, the transfer material P electrostatically holding the toner image is separated from the photoreceptor 1 by the separation charger 8, and is conveyed to the fixing device 6, where the transfer material P is fixed. The toner electrostatically held thereon is thermally fixed to the transfer material P by heating, and the image formation on the transfer material P is completed.

The transfer residual toner remaining on the photosensitive member 1 without being collectively transferred by the transfer charger 7 is removed by the cleaner 5 and collected as waste toner.

A potential corresponding to the electrostatic latent image remains on the surface of the photoconductor 1 after passing through the transfer charger 7, and the residual potential is removed by the neutralizer 2.
With the rotation of, the sheet is again conveyed to the charging section by the charger 3, and image formation is repeatedly performed.

Hereinafter, the charging step and the developing step of the operation of the above-described image forming apparatus will be described in detail.

FIG. 3 shows the magnetic brush charger 3 shown in FIG.
It is a figure which shows one structural example.

The magnetic brush charger 3 is, as shown in FIG.
An opening is provided in a portion close to the photoconductor 1, and a charging container 34 for accommodating the conductive magnetic particles 35 for charging, and the photoconductor 1 is rotatably provided in the opening provided in the charging container 34. The magnet 32
Is fixed, and the magnetic force of the magnet 32 carries the charging conductive magnetic particles 35 on the surface, and the charging sleeve 31 forming the magnetic brush of the charging conductive magnetic particles 35 and the photosensitive member 1 are charged. The charging unit 31 is provided at a predetermined interval downstream of the charging sleeve 31 in the rotation direction with respect to the charging unit Y, and regulates the layer thickness of the conductive magnetic particles 35 for charging carried on the surface of the charging sleeve 31. And a blade 33 that performs the operation.

The magnet 32 fixed inside the charging sleeve 31 is provided at a position substantially opposed to the photosensitive member 1.
And a band electrode S1 for generating a magnetic field with the photoconductor 1, a magnetic pole N2 located downstream of the band electrode S1 in the rotation direction of the charging sleeve 31, and a belt for transporting the conductive magnetic particles 35 for charging. A band electrode S1 having a magnetic pole S2 and a magnetic pole N1;
As a result, a magnetic brush of the conductive magnetic particles 35 for charging is formed on the charging sleeve 31 by a magnetic field generated between the charging sleeve 31 and the photoconductor 1.

In the configuration example shown in FIG. 3, the charging sleeve 31 has an outer diameter of 16 mm, is arranged at an interval of about 500 μm with respect to the photosensitive member, and is opposite to the photosensitive member 1 in the opposite direction. It is spinning. The amount of the magnetic particles 35 for charging in the charging section Y is about 15
It is adjusted to be 0 mg / cm ² .

The outer diameter of the charging sleeve is preferably small in order to make the whole apparatus compact, preferably 25 mm or less, more preferably 10 to 20 mm.

Further, when the charging sleeve having a small diameter as described above is used, in order to increase the chances of contact with the surface of the photoreceptor and to uniformly charge the surface of the photoreceptor, the charging sleeve is formed on the surface of the photoreceptor. It is necessary to rotate at a high speed in the direction opposite to the moving direction (counter direction), preferably 70 to 40
By rotating at 0 rpm, more preferably at 140 to 280 rpm, uniform charging can be performed.

When the photosensitive member is charged while being rotated at a high speed in the counter direction using the small-sized charging sleeve as described above, the conductive magnetic particles at the tip of the magnetic brush carried on the surface of the charging sleeve are removed. Although it is easy to separate and adhere to the surface of the photoreceptor and be easily collected and accumulated in the developing container, in the present invention, the frictional charging imparting property to the toner between the conductive magnetic particles for charging and the magnetic carrier particles for developing is as described above. By setting the triboelectric charge amounts Q1 and Q2 of the toner to satisfy a specific relationship, it is possible to particularly effectively implement an image forming method in which the charging step is performed by rotating the small-diameter charging sleeve at a high speed. .

Hereinafter, the operation of the charger configured as described above will be described in detail.

The conductive magnetic particles for charging 35 accommodated in the charging container 34 are conveyed toward the charging section Y with the rotation of the charging sleeve 31. In the transportation process, the conductive magnetic particles 35 for charging carried on the charging sleeve 31
Is regulated by the blade 33.

Here, a charging bias voltage obtained by superimposing a DC voltage of -650 V and an AC voltage composed of a sine wave is applied to the charging sleeve 31 from a power supply (not shown). 1 is uniformly charged to about -650V.

It has been confirmed that when a charging bias voltage in which an AC voltage is superimposed on a DC voltage is applied to the charging sleeve 31, the charging property is greatly improved, and a longer life of the charger 3 can be achieved. As the optimum range of the AC voltage, Vpp is preferably 500 V or more, more preferably 700 V or more, and further preferably 700 to 100.
0V, and the frequency is preferably 300-5000H
z, more preferably in the range of 500 to 2000 Hz.

When the transfer residual toner remaining on the surface of the photoreceptor 1 reaches the charging section Y, the transfer residual toner is taken into the charging conductive magnetic particles 35 carried on the charging sleeve 31 while being charged by the charging device. 3 and is returned to the normal negative polarity, which is the normal charging polarity, by stirring with the charging magnetic particles 35, and thereafter, the potential difference between the DC voltage applied to the charging sleeve 31 and the surface potential of the photoconductor 1. Is discharged again onto the photoconductor 1.

The following are conceivable as the conductive magnetic particles 35 for charging used in the above-described magnetic brush charger. Magnetic particles such as resin and magnetite are kneaded to form particles, or magnetic particles mixed with conductive carbon to adjust the resistance during kneading. Sintered magnetite, ferrite, or magnetic particles whose resistance has been adjusted by reducing or oxidizing them. The coating material (for example,
Coated with a phenolic resin) or plated with a metal such as Ni to control the resistance to an appropriate value.

If the resistance value of these magnetic particles is too high, charges cannot be uniformly injected into the photoreceptor, resulting in a fog image due to minute charging failure. On the other hand, if it is too low, when there is a pinhole on the surface of the photoreceptor, current concentrates on the pinhole and the charging voltage drops, so that the surface of the photoreceptor cannot be charged, resulting in charging nip-shaped charging failure.

Therefore, the volume resistance of the magnetic particles is
Generally, it is good to be 1 × 10 ² to 1 × 10 ¹⁰ Ω,
More preferably, in consideration of the presence of a pinhole on the photosensitive drum, 1 × 10 ⁶ to 1 × 10 ¹⁰ Ω
Good to be. The volume resistance of the magnetic particles was measured by placing 2 g of the magnetic particles in a metal cell (bottom area: 228 mm ² ) to which a voltage could be applied, applying a weight, and applying a voltage of 100 V.

Regarding the magnetic properties of the conductive magnetic particles for charging, it is better to increase the magnetic restraining force in order to minimize the adhesion of the charged magnetic particles to the drum, and the saturation magnetization is preferably 100 (emu / cm ³ ). Above, more preferably, 15
Desirably, it is 0 to 300 (emu / cm ³ ).

If the average particle size is less than μm, there arises a problem that the charged magnetic carrier tends to adhere to the photosensitive drum during charging.

When the thickness exceeds 80 μm, charging failure in a micro area is apt to occur, and in a cleanerless system, particularly when toner accumulates in a charger to some extent in the latter half of the endurance, it tends to occur remarkably.

Next, the developing step will be described. As a developing method used in the image forming method of the present invention, a two-component developer in which toner particles and magnetic carrier particles are mixed, which has high resolution and is easy to obtain a halftone image, is used in a state of contact with the photosensitive drum. The two-component contact developing method for development is preferable because high image quality can be formed in a full-color copying machine or the like.

FIG. 2 is a diagram showing an example of the configuration of the developing device 4 shown in FIG. 1, and FIG. 2A is a diagram showing the internal configuration.
FIG. 2B is a view of the internal configuration shown in FIG.

In the developing device 4 shown in FIG. 2, a two-component developer prepared by mixing a non-magnetic toner and magnetic carrier particles for development is used as a developer, and the two-component contact developing method is used. Development takes place.

The developing device 4 includes, as shown in FIG.
An opening is provided in a portion close to the developing container 16, and a developing container 16 for accommodating the developer 19 is rotatably incorporated in the opening provided in the developing container 16, and the magnet 12 is fixed inside the developing container 16. A developing sleeve 21 that carries the developer 19 on the surface by the magnetic force of the developer and forms a magnetic brush of the developer 19, and is provided at a predetermined interval above the developing sleeve 21. And a blade 15 for regulating the layer thickness of the carried developer 19. During development, a developing bias voltage is applied to the developing sleeve 21 from a power supply (not shown),
A potential difference occurs between the developing bias voltage applied to the developing sleeve 21 and the surface of the photoconductor 1, and the toner on the developing sleeve 21 is developed on the photoconductor 1 by the potential difference.

Here, the developer 19 is a two-component developer in which the weight ratio of the toner to the magnetic carrier particles for development is 4 to 10%, preferably 6 to 10%.
The toner is a non-magnetic toner charged to a negative (negative) polarity. The toner has a volume average particle size of 2 to 15 μm, preferably 5 to 15 μm, and the magnetic carrier particles for development are made of ferrite particles whose surface is coated with a resin or resin particles in which a magnetic substance is dispersed. And a volume average particle size of 10 to 60 μm, preferably 25
〜60 μm, volume resistivity 10 ⁶ -10 ¹² Ω · cm, and magnetic permeability 2.5-5.0.

The developing container 16 is provided with a toner storage chamber R3 having a supply port 20 through which the replenishment toner 18 is stored and through which the replenishment toner 18 passes when dropped, and a conveying screw 13, and has a stirring chamber inside. A developing chamber R in which the developer 19 transported from R2 is transported along the longitudinal direction of the developing sleeve 21 and carried on the developing sleeve 21.
1, a supply screw 14 and a replenishing toner 18 and a developer 19 that fall freely from the toner storage chamber R3 inside.
Are agitated by the conveying screw 14 so that the developing sleeve 2
1 stirrer chamber R in which the work of transporting along the longitudinal direction is performed
The developing chamber R1 and the stirring chamber R2 are partitioned by a partition wall 17.

In the developing device shown in FIG. 2, the developing sleeve 21 is made of a non-magnetic material and has an outer diameter of 32 mm. The photosensitive member 1 is arranged at an interval of 500 μm, has a peripheral speed of 280 mm / sec, and is rotationally driven in the forward direction of the surface movement of the photosensitive member 1.

The magnet 12 fixed inside the developing sleeve 21 is provided at a position substantially opposed to the photosensitive member 1,
And a magnetic pole N3 provided downstream of the developing pole S1, a magnetic pole N2, a magnetic pole S2, and a magnetic pole N1 provided for transporting the developer 19. A magnetic brush of the developer 19 is formed on the developing sleeve 21 by a magnetic field generated between the developing sleeve 21 and the photoconductor 1 by the developing pole S1.

The blade 15 is made of aluminum, SUS3
16 and is fixed to the developing container 16 such that the distance from the developing sleeve 21 is approximately 800 μm.

The outer diameter of the developing sleeve is preferably small to make the whole apparatus compact, preferably 35 mm or less, more preferably 10 to 25 mm.

The closest distance between the surface of the developing sleeve and the surface of the photoreceptor 1 is preferably 200 to 1000 μm, more preferably 300 to 800 μm, and the distance between the surface of the developing sleeve 21 and the tip of the blade 15 is good. The closest interval is 200 to 800 μm, more preferably 200 to 5 μm.
It is good to be 00 μm.

Hereinafter, the developing device 4 configured as described above will be described.
The operation of will be described.

The surface of the photoreceptor 1 is charged with a charger 3 (see FIG. 1).
It is assumed that an electrostatic latent image is formed which is uniformly charged to, for example, a potential of about -650 V and the surface potential of the image portion is attenuated to, for example, -200 V by the exposure means 11 (see FIG. 1).

The developer 19 conveyed along the longitudinal direction of the developing sleeve 21 by the rotation of the conveying screw 13 inside the developing chamber R 1 is moved to the magnetic pole N 2 of the magnet 12.
It is carried on the developing sleeve 21 at a nearby position, and is conveyed in the direction of the developing unit X by the rotation of the developing sleeve 21.

Next, the thickness of the developer 19 carried on the developing sleeve 21 is regulated by the blade 15, and thereafter, the developer 19 is formed by the magnetic force of the magnetic pole S 1 of the magnet 12 near the developing section X. The magnetic particles for development rise from the developing sleeve 21 while being connected, and a magnetic brush of the developer 19 is formed on the developing sleeve 21.

A developing bias voltage in which an AC voltage is superimposed on a DC voltage is applied to the developing sleeve 21 from a power supply (not shown).
Vpp = 2000V, frequency = 2000 as AC voltage
Hz square wave is applied.

As a result, the surface of the photoreceptor 1 is
Is charged uniformly to -650 V, and then exposed to a laser beam by the exposure means 11 to reduce the surface potential to -200 V.
A potential difference (contrast potential) of 300 V is generated between the surface potential of the image portion attenuated to V and the DC voltage −500 V applied to the developing sleeve 21. Here, since the developer 19 carried on the developing sleeve 21 is stirred by the conveying screws 13 and 14 inside the stirring chamber R2 and the developing chamber R1, the toner constituting the developer 19 is not The charged polarity is negatively charged due to friction with the magnetic particles. Therefore, the toner carried on the developing sleeve 21 is developed on the image portion on the surface of the photoconductor 1 by the potential difference.

Generally, when a developing bias voltage in which an AC voltage is superimposed is applied to the developing sleeve 21, the developing efficiency is increased and a high-quality image can be obtained. However, there is a problem that image fog is easily generated. Would. In order to solve this problem, a potential difference (fogging potential) is usually provided between the DC voltage applied to the developing sleeve 21 and the surface potential of the non-image portion of the photoreceptor 1 to prevent image fogging. Is being done. In this configuration example, the surface potential of the non-image portion on the surface of the photoconductor 1 is −650 V and the developing sleeve 21
15 which is the potential difference from the DC voltage −500 V applied to
0 V corresponds to the fogging potential.

On the other hand, when the toner is consumed by developing the electrostatic latent image formed on the surface of the photoreceptor 1, the replenishing toner 18 stored in the toner storage chamber R3 is replenished based on the consumed amount of the toner. The developer is dropped from the opening 20 and supplied to the stirring chamber R2. The developer is conveyed to the developing chamber R1 while being stirred with the developer 19 by the conveying screw 14 provided in the stirring chamber R2. The toner is conveyed along the longitudinal direction of the developing sleeve 21, and is carried on the developing sleeve 21 at a position near the magnetic pole N <b> 2 in the magnet 12, and is used as toner for forming an image after the next image.

In the above-described image forming method of the present invention, it is also preferable that the surface of the conductive magnetic particles for charging and the surface of the magnetic carrier particles for development are coated with the same material. It is.

Hereinafter, a mode in which the surfaces of the conductive magnetic particles for charging and the surfaces of the magnetic carrier particles for development are coated with the same material will be described in detail.

The method for producing the conductive magnetic particles for charging and the magnetic carrier particles for development includes (i) a method of polymerizing a magnetic metal oxide such as a binder resin, magnetite and the like and a non-magnetic metal oxide. Or (ii)
The core of the magnetic particles is formed by sintered magnetite, ferrite, or a method of reducing or oxidizing the magnetite and ferrite to adjust the resistance value. A coating is applied to the surface of the core of the generated magnetic particles in order to normalize the triboelectric charging characteristics of the toner. At this time, the surfaces of the conductive magnetic particles for charging and the magnetic carrier particles for development are coated with the same coating agent.
The type of the coating agent to be used is not particularly limited as long as the frictional charging characteristics of the toner used in the present embodiment can be made normal.

As described above, by using the same coating material on the surfaces of the conductive magnetic particles for charging and the magnetic carrier particles for developing, the image forming operation is repeated so that the conductive magnetic particles for charging are placed in the developing device. Even when a small amount is accumulated, the frictional charging property of the toner in the developing device with respect to the charging conductive magnetic particles mixed in the developing device is the same as the frictional charging property with the developing magnetic carrier particles. The charge amount distribution of the toner in the container hardly changes before and after the charging magnetic particles are mixed, so that the occurrence of image fogging and toner scattering can be reduced.

Further, even when the magnetic carrier particles for development are mixed in the charger, the coating material between the surface of the magnetic carrier particles for development and the surface of the conductive magnetic particles for charging accommodated in the charger is changed. Since they are the same, the surface physical property values of both are almost the same, and the stirring property for the transfer residual toner is hardly changed before and after the magnetic carrier particles for development are mixed in the charger, so that the spattering of the discharged toner also occurs. Can be reduced.

It is preferable that the physical property values of the conductive magnetic particles for charging and the magnetic carrier particles for development are all the same. For example, if the volume resistivity is the same, even when the magnetic carrier particles for development are mixed in the charger, it is possible to maintain the charging property without substantially increasing the resistance, and if the magnetization amount is the same, Even when the magnetic carrier particles for development are mixed in the charger, the transportability of the conductive magnetic particles for charging in the charger can be maintained, and the conductive magnetic particles for charging are mixed in the developer. Even in this case, it is possible to maintain the transportability of the developer in the developing device, and it is possible to maintain good chargeability and developability.

Further, if the volume average particle diameter is the same, even if the magnetic carrier particles for development are mixed in the charger, or the conductive magnetic particles for charging are mixed in the developing device, the developing device cannot be used. A change in the agitation properties of the magnetic particles with the respective toners in the container can also be suppressed.

The above physical property values have respective optimum ranges in order to simultaneously maintain good chargeability and developability.

The volume resistivity of the magnetic carrier particles for development and the conductive magnetic particles for charging is preferably 1 × 10 ⁵ to 1 ×.
10 ¹² Ω · cm, more preferably 1 × 10 ⁶ to 1 × 10 ⁹
It is better to be in the range of Ω · cm.

When the resistance value of the conductive magnetic particles for charging is high, the charge cannot be uniformly injected into the photosensitive member, and the charging efficiency is lowered. If the resistance of the particles is high, the counter electrode effect decreases, and the density of the macro image decreases. On the other hand, when the resistance value of the conductive magnetic particles for charging is low,
If pinholes are present on the surface of the photoconductor, current concentrates on the pinholes and the charging voltage drops, making it impossible to charge the surface of the photoconductor, resulting in charging failure in the form of a charging nip. If the resistance of the particles is low, charge injection occurs in the developing section where the development on the photoconductor is performed, and the surface potential of the photoconductor converges to the voltage applied to the developing sleeve and decreases. Fog occurs and the image density decreases.

The magnetic properties of the conductive magnetic particles for charging must be increased by increasing the amount of magnetization in order to prevent the magnetic particles from adhering to the photoreceptor, but the magnetic properties of the magnetic carrier particles for development must be increased. Conversely, if the amount of magnetization is too high, the spikes of the magnetic brush formed by the magnetic particles for development become coarse and hard, so that image defects tend to occur.

Therefore, as magnetic properties of the magnetic carrier particles for development and the conductive magnetic particles for charging, the amount of magnetization in a 1 kOe magnetic field is preferably 50 to 350 emu / c.
m ³ , more preferably 70 to 300 emu / cm ³ .

The average particle size of the conductive magnetic particles for charging is selected in consideration of charging properties, prevention of adhesion to a photoreceptor, and the like. It is necessary to select in consideration of mixing and stirring properties, prevention of adhesion to the photoreceptor, and the like.

Therefore, the average particle diameter of the magnetic carrier particles for development and the conductive magnetic particles for charging is preferably 5
It is good that it is in the range of -80 m, more preferably 10-60 m.

In the present invention, the average particle diameter of the magnetic carrier for development and the conductive magnetic particles for charging is measured by using a dry dispersion unit RODOS (manufactured by JEOL) in a laser diffraction particle size distribution analyzer HELOS (manufactured by JEOL). Used in combination, lens focal length 200mm, dispersion pressure 3.0ba
r, particle size 0.5 μm to 3 under measurement conditions of measurement time 1 to 2 seconds
The range of 50.0 μm was measured by dividing it into 31 channels as shown in Table 1 below, and the 50% particle size (median size) of the volume distribution was defined as the average particle size.

[0100]

[Table 1]

In the present invention, the magnetization amount (emu / cm ³ ) of the magnetic carrier particles for development and the conductive magnetic particles for charging in a magnetic field of 1 KOe was measured. The measurement is performed using an oscillating magnetic field type automatic magnetic property recording device BHV-30 manufactured by Co., Ltd. The magnetic characteristic value of the carrier powder creates an external magnetic field of 1 kOe, and determines the magnetization intensity at that time. The carrier is manufactured in a state of being packed in a cylindrical plastic container so as to be sufficiently dense. In this state, the magnetization moment is measured, the actual weight when the sample is put in is measured, and the magnetization intensity is obtained (emu / g). Magnetization strength (emu / g)
Is multiplied by the true specific gravity to determine the magnetization intensity per unit volume (emu / cm ³ ) of the present invention. The true specific gravity of the carrier used in the present invention is measured using a dry automatic densimeter Acupic 1330 manufactured by Shimadzu Corporation.

In the present invention, the triboelectric charge Q1 (mC / kg) of the toner to the magnetic carrier particles for development and the triboelectric charge Q2 to the conductive magnetic particles of the toner for charging
(MC / kg) is measured by the following method.

A measurement sample left overnight in an environment of 23 ° C. and 50% RH was precisely weighed with 1 g of the toner and 9 g of magnetic carrier particles for development or conductive magnetic particles for charging, and approximately 50 c. c. In a wide-mouth bottle with a lid made of polyethylene having a volume of 0.1 g, thoroughly mix the both measuring devices (hold the hand up and down and shake about 125 times for about 50 seconds).

Next, as shown in FIG. 7, about 2.0 g of the mixture is put in a metal measuring container 62 having a 400-mesh screen 63 at the bottom, and a metal lid 64 is placed. At this time, the weight of the entire measurement container 12 is weighed and set as W1 (g). Next, in the suction device 61 (at least a portion in contact with the measurement container 62 is at least an insulator), the air is suctioned from the suction port 67 and the air volume control valve 66 is adjusted to adjust the pressure of the vacuum gauge 65 to 250 mmHg. In this state, sufficient suction is performed for 5 minutes to remove the sample by suction. The potential of the electrometer 69 at this time is set to V (volt).
Here, reference numeral 68 denotes a condenser, the capacity of which is C (μF), and the weight of the whole measuring container after suction is weighed to be W2 (g). The triboelectric charge (mC / kg) of this toner is calculated as in the following equation.

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

Next, a photosensitive member as an image carrier used in the present invention will be described.

As the photoconductor used in the contact charging method using the magnetic brush charger according to the present invention, an organic photoconductor (OPC photoconductor), Se photoconductor and amorphous silicon (a-Si) photoconductor can be used. However, in the present invention, among the contact charging methods using the magnetic brush method, the injection charging method, which is the best in terms of ozone-less and low power consumption, is used.
Those having a surface layer of ⁶ to 10 ¹² Ωcm are preferable,
In particular, those produced by the following production method are preferably used.

FIG. 5 is a diagram showing an example of the structure of the photosensitive member 1 shown in FIG.

This configuration example has a diameter of 30 m as shown in FIG.
m, a base layer 51 made of aluminum, an undercoat layer 52 provided on the base 51 and preventing generation of moire due to reflection of laser light in the exposure step, and an undercoat layer 52 provided on the undercoat layer 52 and injected from the base 51. A positive charge injection preventing layer 53 for preventing the applied positive charges from canceling out the negative charges charged on the photoreceptor surface; and a charge generation layer provided on the positive charge injection preventing layer 53 to generate a positive / negative charge pair upon exposure. A layer 54, a charge transport layer 55 provided on the charge generation layer 54 and transporting charges generated in the charge generation layer 54, and a charge injection layer 56 provided on the charge transport layer 55 and injecting charges. It is composed of

Here, the undercoat layer 52 is a conductive layer having a thickness of 20 μm, and the positive charge injection preventing layer 53 is made of 1 × 10 ⁶ Ω · cm by using an amilan resin and methoxymethylated nylon.
This is a medium resistance layer having a thickness of about 0.1 μm adjusted to a volume resistivity of about 0.1 μm. The charge generation layer 54 is a layer having a thickness of about 0.3 μm in which a disazo pigment is dispersed in a resin.
5 is a dispersion of hydrazone in polycarbonate resin.
Type semiconductor. The charge injection layer 56 is formed by dispersing low-resistance particles such as SnO _{2 in} a polycarbonate resin to form a 1 × 1
It is a layer having a thickness of about 2 μm adjusted to a volume resistivity of 0 ¹³ Ω · cm.

Note that the volume resistivity of the charge injection layer 56 is 1
The range of × 10 ⁹ to 1 × 10 ¹⁴ Ω · cm is the most preferable range, and by adjusting to this range, the chargeability is improved and a higher quality image can be obtained.

The charge transport layer 55 has an insulating property of 10 ¹⁶ Ω · cm or more in terms of volume resistivity with respect to negative charges given to the photoreceptor during the charging step. Therefore, there is a difference in electrical characteristics from the charge injection layer 56, and the charge injection layer 5
The relationship between the volume resistivity of the charge transport layer 55 and the volume resistivity of the charge transport layer 55 is (volume resistivity of the charge injection layer 56)> (charge transport layer 5).
5 (volume resistivity).

The volume resistivity of each layer of the photoreceptor used in the present embodiment is as follows. Under conditions of a temperature of 23 ° C. and a humidity of 50% RH, metal electrodes are arranged at intervals of 200 μm, and the mixture of each layer is interposed therebetween. , Respectively, to form a film, and a voltage of 100 V is applied between the electrodes for measurement.

Further, it is possible to use not only the above-mentioned organic photoreceptor but also an amorphous silicon photoreceptor, and the use of the amorphous silicon photoreceptor has an advantage that further high durability can be realized.

In the present invention, a cleaner-less system (simultaneous development cleaning) can be realized by using the above-described injection charging method. The cleaner-less system is designed to
No cleaning means is provided between the transfer section and the charging section to contact the surface of the photoreceptor to collect transfer residual toner. The transfer residual toner present on the photoreceptor surface after the transfer step is collected by a developing device. And a system for simultaneously developing the next image formed on the photoreceptor into an electrostatic latent image. This cleaner system does not require the conventional cleaning means and does not generate waste toner, and is a system excellent in environmental protection and miniaturization of the image forming apparatus.

The mechanism for collecting the transfer residual toner in the developing device will be described below.

FIG. 6 is a view for explaining a mechanism for collecting the transfer residual toner by the developing device.

FIG. 6 is a modification of the image forming apparatus shown in FIG. 1 in which the static eliminator 2 and the cleaner 5 are removed.

The surface of the photoreceptor 1 is uniformly charged by the charger 3 to a potential of about -650 V.
It is assumed that the surface potential of the image portion is attenuated to about -200 V by 1 to form an electrostatic latent image.

The developing device 4 employs a two-component contact developing method, in which a DC voltage of -500 V is applied from a power supply (not shown).
A developing bias voltage on which an AC voltage which is a rectangular wave having a pp = 2000 V and a frequency = 2000 Hz is superimposed is applied.
It is assumed that development is performed by the reversal development method described above.

First, the untransferred toner is charged to the charger 3 and the photosensitive member 1.
In the charging section Y between the charging device 3 and the charging device 3
The charge polarity of the transfer residual toner is returned to a normal charge polarity (negative polarity) by stirring with the conductive magnetic particles for charging constituting the toner. Using the potential difference with the surface potential,
The transfer residual toner that has been returned to the normal charging polarity is discharged onto the photoconductor 1.

Here, the transfer residual toner discharged onto the photosensitive member 1 forms an electrostatic latent image on the surface of the photosensitive member 1 by the exposure means 11 in the next step, so that an image area on the photosensitive member 1 is formed. And a non-image part. The non-image portion is a portion which is uniformly charged by the charger 3b and is charged to a surface potential of about -650V, and the image portion is a portion which is uniformly charged by the charger 3 to about -650V. ,
The portion where the surface potential has been attenuated to about -200 V due to the irradiation of the laser beam by the exposure means 11.

Next, when the transfer residual toner present in the non-image portion and the image portion reaches the developing portion X, the transfer residual toner present in the image portion remains on the photosensitive member 1. ,
The image is transferred by the transfer charger 7 and contributes as the next image. On the other hand, the transfer residual toner existing in the non-image portion is
The toner is electrostatically collected in the developing device 4 by a fog removal potential of 150 V which is a potential difference between a DC voltage of -500 V applied to the developing sleeve 21 and a surface potential of -650 V of the photoconductor 1.

At this time, in the developing device 4, the developing operation for the electrostatic latent image of the next image is performed at the same time as the operation of collecting the transfer residual toner.

As a condition for reliably performing the operation of collecting the transfer residual toner, it is necessary that the charge polarity of the transfer residual toner in the developing unit X (collection unit) is the same as that of the toner in the developing device 4b. In the present invention, in the charging device 3, the charging polarity of the transfer residual toner charged to the opposite polarity to the charging polarity of the toner in the developing device 4 is returned to the same charging polarity as the toner in the developing device 4, An operation for adjusting the charge polarity of the transfer residual toner to the normal charge polarity is performed.

[0126]

Next, the present invention will be described more specifically with reference to examples and comparative examples.

(Embodiment 1) The image forming apparatus shown in FIG.
Using the negative charging photoreceptor having the above-described charge injection layer shown in FIG. 5, the magnetic brush charger shown in FIG. 3, and the two-component contact developing type developing device shown in FIG. An image was formed under development conditions and a charging sequence, and fog on the transfer paper and toner scattering were evaluated.

Charging conditions: * Conductive magnetic particle material: core; ferrite, coating material; silicon-based resin * Volume resistivity of conductive magnetic particles: 1 × 10 ⁶ Ω · cm * Average particle size of conductive magnetic particles ... 30 µm * Saturation magnetization of conductive magnetic particles ... 200 emu / cm ³
(In a magnetic field of 1 KOe) * Charging sleeve outer diameter: diameter 16 mm * Charging sleeve rotation speed: 168 rpm (in a direction opposite to the moving direction of the photoconductor surface) * Magnetism of the magnet in the charging sleeve: 4 poles shown in FIG. Charging bias DC component: -650 V AC component: 700 V _PP , 1000 Hz * Surface potential of charged photoreceptor: -650 V Development condition: developer: polyester resin as a main component,
A two-component developer having a chargeable non-magnetic toner having a colorant and a negative charge control agent and resin-coated ferrite carrier particles having a ferrite carrier core surface treated with a silicone resin (toner concentration: 6% by weight) * magnetic carrier Volume resistivity of particles: 5 × 10 ⁶ Ω · cm * Average particle size of magnetic carrier particles: 35 μm * Saturation magnetization of magnetic carrier particles: 140 emu / cm ³
(In a magnetic field of 1 KOe) * Outer diameter of developing sleeve: diameter 16 mm * Rotation speed of developing sleeve: 210 rpm (forward direction with respect to moving direction of photoconductor surface) * Magnetic pole of magnet in developing sleeve: 5 shown in FIG. Extreme * DC component for developing bias: -500 V AC component: 2000 V _pp , 2000 Hz * Bright part potential: -200 V * Closest distance between developing sleeve surface and photoreceptor surface: 50
0 μm * The closest distance between the active sleeve surface and the blade: 800
μm • Charging series (toner triboelectric charge): conductive magnetic particles,
The magnetic carrier particles and the toner are all an initial agent at 23 ° C./50% RH by a two-component blow-off method. H. Was measured under the following environment. * Amount of frictional charge of toner on conductive magnetic particles for charging ...
-22 mC / kg * Amount of triboelectric charge of toner with respect to carrier particles for development ...-
22mC / kg

When the image was formed under the above conditions,
Even when the image forming operation of 50,000 sheets was repeated, no fog was found (level A according to the fog evaluation method described later), an image density of 1.5 or more was obtained, and a good image without toner scattering was obtained. The amount of conductive magnetic particles for charging mixed in the developing container after forming 50,000 sheets of image was 10% by weight based on the total weight of the magnetic carrier particles for developing existing in the developing container. Was.

Fog was determined by the following method. That is, TOKYO KENSHOKU CO. The reflection density of each of the fogged portion on the transfer paper and the transfer paper before image formation was obtained from DENSI OMETER C-6DS of LTD, and was calculated by the following equation (3).

Fog density (%) = (reflection density of fog portion on transfer paper) − (reflection density of transfer paper) (Equation 3) <Evaluation criteria> Level A: Fog density <0.5: Virtually no fog. Level B: 0.5 ≦ fog density <1: almost no fog. Level C: 1 ≦ fog density <2 slightly fog. Level D: 2 ≦ fog density <3: fog is present. Level E: 3 ≦ fog density: fairly fog.

Regarding the image density, the reflection density of the image on the transfer paper was measured using a density system 941 manufactured by X-rite.

(Embodiment 2) The image forming apparatus shown in FIG.
Using the following a-Si photoreceptor for positive charging, the magnetic brush charger shown in FIG. 3, and the developing device of the two-component contact developing system shown in FIG. To form an image, and evaluation of fog and toner scattering on the transfer paper was performed.

Photoreceptor: * Volume resistivity of surface layer of photoreceptor: 1 × 10 ^-14 Ω · cm Charging condition: Conductive magnetic particle material: Core; ferrite, coating material; Volume resistivity of conductive magnetic particles: 1 × 10 ⁶ Ω · cm * Average particle size of conductive magnetic particles: 30 μm * Saturation magnetization of conductive magnetic particles: 200 emu / cm ³
(In a magnetic field of 1 KOe) * Charging sleeve outer diameter: 16 mm in diameter * Rotating speed of charging sleeve: 280 rpm (in a direction opposite to the moving direction of the surface of the photoconductor) * Magnetism of a magnet in the charging sleeve: 4 poles shown in FIG. * Charging bias DC component: +650 V AC component: 700 V _PP , 1000 Hz * Surface potential of charged photoreceptor: +650 V-Developing conditions: developer: a styrene / acrylic resin as a main component, a colorant and a negative charge control agent A two-component developer having a negatively-chargeable non-magnetic toner and magnetic material-dispersed resin carrier particles obtained by dispersing magnetite and hematite on a phenolic resin and coating the surface of the magnetic material-dispersed carrier core with a silicone resin coating ( Rights of the toner concentration of 6 wt%) * volume resistivity of the magnetic carrier particles ^{... 1 × 10 10 Ω · cm} * magnetic carrier particles The saturation magnetization of the particle size ... 35μm * magnetic carrier particles ... 100emu / cm ³
(In a magnetic field of 1 KOe) * Outer diameter of developing sleeve: diameter 32 mm * Rotation speed of developing sleeve: 300 rpm (forward direction with respect to moving direction of photoconductor surface) * Magnetic pole in developing sleeve: 5 shown in FIG. Pole * DC component for developing bias: +500 V AC component: 2000 V _pp , 2000 Hz * Bright portion potential: +200 V * Closest distance between developing sleeve and photoconductor: 500 μm * Nearest distance between active sleeve and blade: 800 μm Triboelectric charge of toner): conductive magnetic particles,
The magnetic carrier particles and the toner are all an initial agent at 23 ° C./50% RH by a two-component blow-off method. H. Was measured under the following environment. * Amount of frictional charge of toner on conductive magnetic particles for charging ...
-22 mC / kg * Amount of triboelectric charge of toner with respect to carrier particles for development ...-
22mC / kg

When the image was formed under the above conditions,
Even when the image forming operation of 50,000 sheets was repeated, there was almost no fog (level B in the above-described fog evaluation method), an image density of 1.5 or more, and a good image with almost no toner scattering was obtained. The amount of the conductive magnetic particles for charging mixed in the developing container after forming 50,000 sheets of images was 14% by weight based on the total weight of the magnetic carrier particles for developing existing in the developing container. Was.

Example 3 Example 1 was repeated except that the conductive magnetic particles of the magnetic brush charger and the magnetic carrier particles for development of the two-component developer were changed to those shown below. Evaluation was performed in the same manner as in Example 1.

(Conductive Magnetic Particles) * Conductive magnetic particle material: core: ferrite, coating material;
Acrylic resin coating * Volume resistivity of conductive magnetic particles: 1 × 10 ⁶ Ω · cm * Average particle size of conductive magnetic particles: 30 μm * Saturation magnetization of conductive magnetic particles: 200 emu / cm ³
(In a magnetic field of 1 KOe)

(Magnetic Carrier Particles) * Magnetic carrier particle material: Magnetic material dispersed resin carrier in which magnetite and hematite are dispersed in a phenol resin and the surface of a magnetic material dispersed carrier core is coated with a silicone resin * Volume resistance of particles of the magnetic carrier Rate: 1 × 10 ¹⁰ Ω · c
m * Average particle diameter of magnetic carrier particles: 40 μm * Saturation magnetization of magnetic carrier particles: 300 emu / cm ³
(In a magnetic field of 1 KOe)

The amount of frictional charge of the toner with respect to the conductive magnetic particles for charging and the magnetic carrier particles for development is shown below.

Charging series (amount of triboelectric charging): conductive magnetic particles, magnetic carrier, and toner were all used as an initial agent and a two-component blow-off method at 23 ° C./50% R.F. H. Was measured under the following environment. * Amount of frictional charge of toner with respect to conductive charging magnetic particles ...
-27 mC / kg * Amount of triboelectric charge of toner with respect to magnetic carrier particles for development: -20 mC / kg

As a result of evaluation, when the image forming operation for 50,000 sheets was repeated, fog was found to be slight (level C according to the above-mentioned fog evaluation method), but the image density was 1.5 or more.
A good image having no practical problem with respect to toner scattering was obtained. The amount of conductive magnetic particles for charging mixed in the developing container after forming 50,000 sheets of images was 15% by weight based on the total weight of the magnetic carrier particles for developing existing in the developing container. Was.

Comparative Example 1 The procedure of Example 1 was repeated except that the conductive magnetic particles of the magnetic brush charger and the magnetic carrier particles for development of the two-component developer were changed to those shown below. Evaluation was performed in the same manner as in Example 1.

(Conductive Magnetic Particles) * Conductive magnetic particle material: core: ferrite, coating material;
Silicon resin coating * Volume resistivity of conductive magnetic particles: 1 × 10 ⁶ Ω · cm * Average particle size of conductive magnetic particles: 22 μm * Saturation magnetization of conductive magnetic particles: 200 emu / cm ³
(In a magnetic field of 1 KOe) (Magnetic carrier particles) * Magnetic carrier particle material: Magnetic material-dispersed resin carrier obtained by dispersing magnetite and hematite in phenolic resin and coating the surface of the magnetic material-dispersed carrier core with an acrylic resin * Magnetic carrier particles * 1 × 10 ¹⁰ Ω · cm * Average particle size of magnetic carrier particles: 33 μm * Saturation magnetization of magnetic carrier particles: 140 emu / cm ³
(In a magnetic field of 1 KOe) The frictional charge amount of the toner with respect to the conductive magnetic particles for charging and the magnetic carrier particles for development is shown below.

Charging series (frictional charge of toner): conductive magnetic particles, magnetic carrier particles, and toner are all an initial agent,
23 ° C / 50% R. H. Was measured under the following environment. * Amount of frictional charge of toner on conductive magnetic particles for charging ...
-16 mC / kg * Amount of frictional charge of toner with respect to magnetic carrier particles for development: -27 mC / kg

The evaluation results show that, when the image forming operation for 20,000 sheets is repeated, fogging occurs (level D in the above-described fog evaluation method), only an image density of 1.3 is obtained, toner scattering increases, and A defect has occurred. The amount of conductive magnetic particles for charging mixed in the developing container after forming 20,000 sheets of images was 18% by weight based on the total weight of the magnetic carrier particles for developing existing in the developing container. Was.

(Example 4) In Example 1, the outer diameter of the charging sleeve of the magnetic brush charger was changed to a diameter of 12 mm, and the rotation speed of the charging sleeve was changed to 278 rpm.
The evaluation was performed in the same manner as in Example 1 except that the direction was changed to the direction opposite to the moving direction of the photosensitive member surface.

As a result of evaluation, when the image forming operation of 50,000 sheets was repeated, fog was slightly observed (fog level C), but the image density was 1.5 or more, and there was no practical problem with toner scattering. Good images were obtained.

The amount of conductive magnetic particles for charging mixed in the developing container after forming 50,000 sheets of image was 19% by weight based on the total weight of the developing magnetic carrier particles present in the developing container. %Met.

Comparative Example 2 The procedure of Example 4 was repeated except that the conductive magnetic particles of the magnetic brush charger and the magnetic carrier particles for development of the two-component developer were changed to those shown below. Evaluation was performed in the same manner as in Example 4.

(Conductive Magnetic Particles) * Material of conductive magnetic particles: 10 parts of MgO, 10 parts of MnO,
After 80 parts of Fe ₂ O ₃ were each made into fine particles, water was added and mixed, and carbon black was added to the granulated product.
A partially coated vinylidene fluoride / methyl methacrylate copolymer coated so that the coating amount is 1 part. * Volume resistivity of conductive magnetic particles: 6 × 10 ⁶ Ω · cm * Average particle size of conductive magnetic particles: 28.5 μm * Saturation magnetization of conductive magnetic particles: 150 emu / cm ³
(In a magnetic field of 1 KOe)

(Magnetic Carrier Particles) * Magnetic Carrier Material: Same as in Example 3 * Volume Resistivity of Magnetic Carrier Particles: 4 × 10 ¹² Ω · cm * Average Particle Size of Magnetic Carrier Particles: 33 μm Saturation magnetization: 137 emu / cm ³
(In a magnetic field of 1 KOe)

The frictional charge of the toner with respect to the above-described conductive magnetic particles for charging and the magnetic carrier particles for development is shown below. -Charging series (frictional charge of toner): conductive magnetic particles,
The magnetic carrier particles and the toner are all an initial agent at 23 ° C./50% RH by a two-component blow-off method. H. Was measured under the following environment.

* Amount of frictional charge of toner with respect to conductive magnetic particles for charging: -16 mC / kg * Amount of frictional charge of toner with respect to magnetic carrier particles for development ... -27 mC / kg As a result of the evaluation, the image forming operation of 50,000 sheets is repeated. Fog (level D), an image density of only 1.3 was obtained, toner scattering increased, and image defects occurred.

The amount of conductive magnetic particles for charging mixed in the developing container after forming an image of 50,000 sheets was 18% by weight based on the total weight of the magnetic carrier particles for developing existing in the developing container. %Met.

Example 5 FIG. 1 used in Example 1
Instead of the image forming apparatus shown in FIG. 1, a cleaner-less type image forming apparatus having no cleaner shown in FIG. 6 is used. After being taken in, it is discharged from the magnetic brush onto the photoreceptor, and in the same manner as in Example 1, except that the photoreceptor is moved and collected in the developing container in the developing area. An evaluation was performed.

As a result of evaluation, even when the image forming operation of 50,000 sheets was repeated, no fog was found (level A), the image density was 1.5 or more, and a good image without toner scattering was obtained. The amount of conductive magnetic particles for charging mixed in the developing container after forming 50,000 sheets of image was 10% by weight based on the total weight of the magnetic carrier particles for developing existing in the developing container. Was.

Further, the toner consumption efficiency when 50,000 images having an image area ratio of 50% were formed on an A4 size recording material was improved by 20% as compared with the case of the image forming apparatus of the first embodiment.

Embodiment 6 The image forming apparatus shown in FIG. 1 has a negatively chargeable organic photosensitive member having a charge injection layer shown in FIG. 5, a magnetic brush charger shown in FIG. 3, and a two-component shown in FIG. Using a developing device of a system contact development system, the following charging conditions, the developing conditions and the physical property value of the conductive magnetic particles for charging, the physical property value of the magnetic carrier particles for development, the image forming operation of 50,000 sheets is repeated, The above evaluation of image fog, image density and toner scattering was performed in the same manner as in Example 1.

<Charging Conditions> * Conductive magnetic particles for charging: core; ferrite (280e
mu / cm ³ ), coating material; silicone resin, volume resistivity: 1 × 10 ⁷ Ω · cm, average particle size: 28 μm, saturation magnetization: 280 emu / cm ³ (in a magnetic field of 1 KOe) * Charging sleeve: outer diameter Diameter 16 mm, rotation speed 16
8 rpm (in the direction opposite to the direction of movement of the photoreceptor surface), magnetic poles of the magnet; 4 poles shown in FIG. 3 * Charging bias: DC voltage: -650 V, AC voltage: 7
00Vpp, 1000Hz

<Developing Conditions> * Developer ・ Developing toner: a non-magnetic toner containing a polyester resin as a main component and having a coloring material and a negative charge controlling agent ・ Developing magnetic carrier particles: core; ferrite (280)
emu / cm ³ ), coating material; silicon-based resin (same material as coating material of conductive magnetic particles for charging), volume resistivity;
1 × 10 ⁷ Ω · cm (average particle size: 28 μm, saturation magnetization;
140 emu / cm ³ (in a magnetic field of 1 KOe) ・ Mixing ratio: toner concentration in developer 8% * Developing sleeve: outer diameter: 16 mm, rotation speed 210 rpm
m (forward direction to the moving direction of the photosensitive member surface, magnetic pole of magnet; 5 poles shown in FIG. 2 * Developing bias: DC voltage; -500 V, AC voltage; 2
000 Vpp, 2000 Hz * The closest distance between the surface of the developing sleeve and the surface of the photoconductor; 50
0 μm * The closest distance between the surface of the developing sleeve and the blade; 600
μm

<Photoconductor surface potential> * Image portion potential (bright portion potential): -200 V * Non-image portion potential (dark portion potential): -650 V

<Amount of frictional charge of toner> * Amount of frictional charge of toner with respect to conductive magnetic particles for charging ...
-22 mC / kg * Amount of frictional charge of toner with respect to magnetic carrier particles for development: -22 mC / kg

The amount of triboelectric charging of the toner was determined at a temperature of 23.
The magnetic particles for charging, the magnetic particles for developing, and the toner for developing were all measured in the initial state by a two-component blow-off method under the conditions of ° C. and a humidity of 50% RH.

Under the above conditions, when the image forming operation of 50,000 sheets was repeatedly performed, the image on the transfer paper after 50,000 sheets had no image fog (evaluation criteria;
Level A), an image density of 1.5 or more were obtained, and a good image without toner scattering was obtained. The amount of conductive magnetic particles for charging mixed in the developing container after forming 50,000 sheets of image was 10% by weight based on the total weight of the magnetic carrier particles for developing existing in the developing container. Was.

Example 7 The following positively chargeable amorphous silicon photosensitive member, a magnetic brush charger shown in FIG. 3, and a two-component contact developing system shown in FIG. 2 were added to the image forming apparatus shown in FIG. Using the device, under the following conditions, 5000
The image forming operation for zero sheets was repeated, and the image fog on the transfer material P, the image density, and the toner scattering were evaluated in the same manner as in Example 6. These evaluations were made in Example 6.
Was performed in the same manner as described above.

<Photoreceptor> * Photoreceptor: Volume resistivity of surface layer: 1 × 10 ¹⁴ Ω · cm

<Charging Conditions> * Conductive magnetic particles for charging: core; ferrite (280e
mu / cm ³ ), coating material: fluororesin, volume resistivity: 1 × 10 ⁷ Ω · cm, average particle size: 22 μm, saturation magnetization: 280 emu / cm ³ (in a magnetic field of 1 KOe) * Charging sleeve: outer diameter Diameter 16 mm, rotation speed 17
0 rpm (in the direction opposite to the direction of movement of the photoreceptor surface), magnetic poles of the magnet; 4 poles shown in FIG. 3 * Charging bias: DC voltage: +650 V, AC voltage: 7
00Vpp, 1000Hz

<Developing Conditions> * Developer ・ Developing toner: Non-magnetic toner containing styrene / acrylic resin as a main component and having a colorant and a negative charge controlling agent ・ Development magnetic carrier particles: core; magnetic substance dispersed polymerization Magnetic particles (280 emu / cm ³ ), coating material; fluororesin (same material as coating material of conductive magnetic particles for charging),
Volume resistivity; 1 × 10 ⁹ Ω · cm Average particle size: 28 μm,
Saturation magnetization: 210 emu / cm ³ (in a magnetic field of 1 KOe) Mixing ratio: toner concentration in developer 7% * Developing sleeve: outer diameter: 16 mm, rotation speed 210 rpm
m (forward with respect to the direction of movement of the photoconductor surface, magnetic poles of the magnet; 5 poles shown in FIG. 2 * Developing bias: DC voltage; +500 V, AC voltage;
000 Vpp, 2000 Hz * The closest distance between the surface of the developing sleeve and the surface of the photoconductor; 50
0 μm * The closest distance between the surface of the developing sleeve and the sleeve; 600
μm

<Photoconductor surface potential> * Image portion potential (bright portion potential): +200 V * Non-image portion potential (dark portion potential): +650 V

<Amount of frictional charge of toner> * Amount of frictional charge of toner with respect to conductive magnetic particles for charging ...
+27 mC / kg * Amount of frictional charge of toner with respect to magnetic carrier particles for development ... + 25 mC / kg

Under the above conditions, when the image forming operation of 50,000 sheets was repeatedly performed, the image on the transfer agent P after 50,000 sheets had almost no image fog (evaluation standard; level B) and the image density was 1 0.5 or more, and a good image with almost no toner scattering was obtained. 5000
The amount of conductive magnetic particles for charging mixed in the developing container after the zero-sheet image was formed was 14% by weight based on the total weight of the magnetic carrier particles for developing existing in the developing container. Was.

Comparative Example 3 The procedure of Example 6 was repeated, except that the conductive magnetic particles of the magnetic brush charger and the magnetic carrier particles for development of the two-component developer were changed to those shown below. Evaluation was performed in the same manner as in Example 6. * Conductive magnetic particles for charging: core; ferrite, coating material; titanium coupling agent, volume resistivity: 1 × 10 ^6.
cm, average particle size: 22 μm, saturation magnetization: 280 emu /
cm ³ (in a magnetic field of 1 KOe) * Development magnetic carrier particles: core; magnetic material-dispersed polymerized magnetic particles in which magnetite and hematite are dispersed in phenolic resin; coating material; silicon-based resin coating;
0 ¹⁰ Ω · cm average particle size; 35 μm, saturation magnetization; 180 e
mu / cm ³ (in a magnetic field of 1 KOe) The frictional charge amount of the toner with respect to the conductive magnetic particles for charging and the magnetic carrier particles for development is shown below.

<Amount of frictional charge of toner> * Amount of frictional charge of toner with respect to conductive magnetic particles for charging ...
-16 mC / kg * Amount of triboelectric charge of toner with respect to conductive magnetic particles for development ...
-28 mC / kg

When the image forming operation was repeatedly performed under the above conditions, when the image forming operation of 20,000 sheets was repeated, image fogging occurred (evaluation criterion; level D), and an image density of only 1.3 was obtained. In addition, toner scattering increased, and image defects occurred. The amount of conductive magnetic particles for charging mixed in the developing container after forming 20,000 sheets of images was 25% by weight based on the total weight of the magnetic carrier particles for developing existing in the developing container. Was.

[0175]

According to the above-described structure, the transfer residual toner that has reached the developing portion X has a negative polarity, which is almost a normal charging polarity, and is well collected by the developing device 4b. Can be achieved.

According to the present invention, in the charging step, a small-diameter charging sleeve is used as the charging sleeve of the magnetic brush charger, and the image forming operation is repeatedly performed for a long time while being rotated at a high speed. It is possible to provide a good image without toner scattering.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of an image forming apparatus according to the present invention.

FIGS. 2A and 2B are schematic configuration diagrams of a developing device used in the image forming apparatus shown in FIG. 1, FIG. 2A is a diagram showing an internal configuration, and FIG. 2B is a diagram shown in FIG. It is the figure which looked at the internal configuration which looked at from the upper part.

FIG. 3 is a schematic sectional view of a charging device used in the image forming apparatus of the present invention.

FIG. 4 is a schematic configuration diagram of a laser scanning unit 100 that scans a laser beam in the image forming apparatus of the present invention.

FIG. 5 is a diagram illustrating a configuration example of a photoconductor used in the image forming apparatus illustrated in FIG. 1;

FIG. 6 is a schematic configuration diagram of an embodiment of an image forming apparatus of a type in which a transfer residual toner is collected by a developing device.

FIG. 7 is an explanatory diagram of a measuring device for measuring a triboelectric charge amount of toner.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor drum 3 charger 4 developing device 5 cleaner 6 fixing device 7 transfer charger 8 separation charger 11 developing sleeve 21 developing sleeve 31 charging sleeve 32 magnet 33 blade 34 charging container 35 charging magnetic particle 101 base 102 under Pulling layer 103 Positive charge injection preventing layer 104 Charge generation layer 105 Charge transport layer 106 Charge injection layer X Developing part Y Charging part

Continued on the front page (72) Inventor Masanori Shida 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Ichiro Ozawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. F-term (reference) 2H003 AA02 BB11 CC04 2H005 BA02 BA03 BA06 BA11 DA07 DA09 EA01 EA02 EA05 FA01 2H031 AC01 AC15 AC19 AC30 AD03 AD09 AE01 BA04 BB01 CA11 2H077 AA11 AA37 AC02 AC16 AD02 AD06 AD13 AD36 AE06 GA17

Claims (76)

[Claims] 1. A conductive magnetic particle, a rotatable conductive magnetic particle carrier for carrying and transporting the conductive magnetic particle, and a plurality of magnetic particles provided inside the conductive magnetic particle carrier. Applying a voltage to the conductive magnetic particle carrier, and bringing the conductive magnetic particles into contact with the image carrier, thereby causing the surface of the image carrier to A charging step of charging; (B) a latent image forming step of forming an electrostatic latent image on the surface of the charged image carrier; and (C) a toner image and a magnetic carrier particle which are opposed to the image carrier. Using a developing device having a two-component developer, a developer carrier for carrying the two-component developer, and a plurality of magnetic field generating means provided inside the developer carrier, An alternating electric field is formed at a portion where the image carrier and the developer carrier face each other, and the two-component system A developing step of forming a toner image by developing the electrostatic latent image with a toner as an agent, the frictional charge (Q1) of the toner with the conductive magnetic particles
And the triboelectric charge (Q2) of the toner with the magnetic carrier particles in the developing device has the following relationship: 0 <Q2 ≦ Q1 (mC
/ Kg) or 0> Q2 ≧ Q1 (mC / kg). 2. The conductive magnetic particle carrier according to claim 1, wherein the carrier has a cylindrical shape having an outer diameter of 25 mm or less, and rotates at a rotation speed of 70 to 400 rpm in a charging step. Image forming method. 3. The conductive magnetic particle carrier according to claim 1, wherein the carrier has a cylindrical shape with an outer diameter of 10 to 20 mm, and rotates at a rotation speed of 140 to 280 rpm in a charging step. Image forming method. 4. The frictional charge amount (Q1) of the toner with the conductive magnetic particles and the frictional charge amount (Q2) of the toner with the magnetic carrier particles in the developing device have the following relationship: 0 <
Q2 <Q1 (mC / kg) or 0>Q2> Q1 (m
C / kg).
The image forming method according to any one of the above. 5. The frictional charge (Q1) of the toner with the conductive magnetic particles and the triboelectric charge (Q2) of the toner with magnetic carrier particles in the developing device have the following relationship: 5 ≦ 5
| Q1 | ≦ 60 (mC / kg) and 5 ≦ | Q2 | ≦ 60
The image forming method according to claim 1, wherein (mC / kg) is satisfied. 6. The developer carrier has an outer diameter of 35 mm.
6. The following cylindrical shape.
The image forming method according to any one of the above. 7. The developer carrier has an outer diameter of 10 to 2 mm.
6. The image forming method according to claim 1, wherein the image forming method has a cylindrical shape of 5 mm. 8. The developing device has a developing container for holding the two-component developer, and the amount of the conductive magnetic particles mixed in the developing container is held in the developing container. 8. The image forming method according to claim 1, wherein the amount is 20% by weight or less based on the weight of the magnetic carrier particles. 9. The developing device has a developing container for holding the two-component developer, and the amount of the conductive magnetic particles mixed in the developing container is stored in the developing container. 20% by weight or less based on the weight of the magnetic carrier particles used, and the triboelectric charge (Q1) of the toner with the conductive magnetic particles.
And the frictional charge (Q2) of the toner with the magnetic carrier particles in the developing device is expressed by the following relationship: 0 <Q2 <Q1 (mC
The image forming method according to any one of claims 1 to 7, wherein the image satisfies 0 / Q2> Q1 (mC / kg). 10. The developing device has a developing container for holding the two-component developer, and the amount of the conductive magnetic particles mixed in the developing container is stored in the developing container. 20% by weight based on the weight of the magnetic carrier particles used
The frictional charge (Q1) of the toner with the conductive magnetic particles and the triboelectric charge (Q2) of the toner with the magnetic carrier particles in the developing device have the following relationship: 5 ≦ |
Q1 | ≦ 60 (mC / kg) and 5 ≦ | Q2 | ≦ 60
10. The image forming method according to claim 1, wherein (mC / kg) is satisfied. 11. The conductive magnetic particles for charging may be 10 ² to 10 ² .
The image forming method according to claim 1, wherein the image forming method has a volume resistivity of 10 ¹⁰ Ω · cm. 12. The conductive magnetic particles for charging may have a particle size of 10 ⁶ to
The image forming method according to claim 1, wherein the image forming method has a volume resistivity of 10 ¹⁰ Ω · cm. 13. The method according to claim 1, wherein the conductive magnetic particles for charging are 1 KOe.
13. The image forming method according to claim 1, wherein the magnetic field has a saturation magnetization of 100 emu / cm ³ or more in the magnetic field. 14. The conductive magnetic particles for charging are 1 KOe.
14. The image forming method according to claim 1, wherein the magnetic field has a saturation magnetization of 150 to 300 emu / cm ³ in the magnetic field. 15. The conductive magnetic particles for charging may be 5 to 80.
The image forming method according to claim 1, wherein the image forming method has a volume average particle diameter of μm. 16. The conductive magnetic particles for charging may be 10 to 6 particles.
The image forming method according to claim 1, wherein the image forming method has a volume average particle diameter of 0 μm. 17. The conductive magnetic particles for charging have magnetic core particles of resin magnetic particles produced by polymerizing a binder resin, a magnetic metal oxide and a non-magnetic metal oxide. The image forming method according to claim 1. 18. The method according to claim 1, wherein in the charging step, the voltage applied to the conductive magnetic particle carrier is a DC voltage on which an AC voltage is superimposed. Image forming method. 19. Magnetic carrier particles for developing is ¹⁰⁶
The image forming method according to claim 1, wherein the image forming method has a volume resistivity of 10 to 10 ¹² Ω · cm. 20. The magnetic carrier particles for development according to claim 10, wherein
20. The image forming method according to claim 1, having a volume average particle size of 60 [mu] m. 21. The magnetic carrier particles for development according to claim 25, wherein
20. The image forming method according to claim 1, having a volume average particle size of 60 [mu] m. 22. The magnetic carrier particles for development having a carrier core of resin magnetic particles formed by polymerizing a binder resin, a magnetic metal oxide and a non-magnetic metal oxide. 22. The image forming method according to any one of 1 to 21. 23. The image forming apparatus according to claim 1, wherein in the developing step, the voltage applied to the developer carrier is a DC voltage on which an AC voltage is superimposed. Method. 24. The surface of the conductive magnetic particles for charging and the surface of the magnetic carrier particles for development are coated with the same material.
2. The image forming method according to 1., 25. The conductive magnetic particles for charging and the magnetic carrier particles for development are each 10 ⁵ to 10 ¹² Ω · cm.
25. The volume resistivity of claim 24.
2. The image forming method according to 1., 26. The method according to claim 24, wherein the conductive magnetic particles for charging and the magnetic carrier particles for development both have a volume resistivity of 10 ⁶ to 10 ⁹ Ω · cm. Image forming method. 27. The conductive magnetic particles for charging and the magnetic carrier particles for development are all 50 KOe in a magnetic field of 1 KOe.
27. The image forming method according to claim 24, wherein the image forming method has a magnetization of about 350 emu / cm ³ . 28. The conductive magnetic particles for charging and the magnetic carrier particles for development are both 70 μm in a magnetic field of 1 KOe.
27. The image forming method according to claim 24, wherein the image forming method has a magnetization of about 300 emu / cm < ³ >. 29. The conductive magnetic particles for charging and the magnetic carrier particles for development both have a volume average particle size of 5 to 80 μm.
The image forming method according to any one of the above. 30. The conductive magnetic particles for charging and the magnetic carrier particles for development both have a volume average particle diameter of 10 to 60 μm.
9. The image forming method according to any one of items 8. 31. The conductive magnetic particles for charging have magnetic core particles of resin magnetic particles produced by polymerizing a binder resin, a magnetic metal oxide and a non-magnetic metal oxide. The image forming method according to claim 24. 32. The method according to claim 24, wherein in the charging step, the voltage applied to the conductive magnetic particle carrier is a DC voltage on which an AC voltage is superimposed. Image forming method. 33. The developing magnetic carrier particles having a carrier core of resin magnetic particles produced by polymerizing a binder resin, a magnetic metal oxide and a non-magnetic metal oxide. 33. The image forming method according to any one of 24 to 32. 34. The image forming apparatus according to claim 24, wherein the voltage applied to the developer carrier in the developing step is a DC voltage on which an AC voltage is superimposed. Method. 35. The image bearing member has a volume resistivity of 10 ⁶ or less.
The image forming method according to any one of claims 1 to 34, further comprising a surface layer of 10 ¹⁴ Ω · cm. 36. An image carrier comprising an organic photoconductor (OP)
The image forming method according to any one of claims 1 to 35, further comprising (C) a photoconductor. 37. The image forming method according to claim 1, wherein the image bearing member has an amorphous silicone (a-Si) photosensitive member. 38. The image forming method further comprises a transfer step of transferring a toner image formed on the image carrier to a transfer material, and after the transfer step and before the charging step. The method does not include a cleaning step for removing the transfer residual toner remaining on the image carrier after the transfer step from the surface of the image carrier, and the transfer remaining on the image carrier after the transfer step. 38. The image forming method according to claim 1, wherein the residual toner is collected by the developing device. 39. (A) a latent image carrier for carrying an electrostatic latent image; (B) conductive magnetic particles, and rotatable conductive magnetic particles carrying and carrying the conductive magnetic particles And a plurality of magnetic field generating means provided inside the conductive magnetic particle carrier, applying a voltage to the conductive magnetic particle carrier, and applying the conductive magnetic particles to the image carrier. (C) a latent image forming means for forming an electrostatic latent image on the charged surface of the image carrier; and A) a two-component developer having a toner and a magnetic carrier facing the image carrier, a developer carrier for supporting the two-component developer, and a developer carrier provided inside the developer carrier. A plurality of magnetic field generating means, and an alternating electric field is formed at a portion where the image carrier and the developer carrier are opposed to each other. A developing device for developing the electrostatic latent image with the toner of the two-component developer to form a toner image; and a triboelectric charge amount of the toner with the conductive magnetic particles ( Q1) and the triboelectric charge (Q) between the toner and the magnetic carrier particles in the developing device.
2) satisfies the following relationship: 0 <Q2 ≦ Q1 (mC / kg) or 0> Q2 ≧ Q1 (mC / kg). 40. The conductive magnetic particle carrier according to claim 39, wherein the conductive magnetic particle carrier has a cylindrical shape with an outer diameter of 25 mm or less, and rotates at a rotation speed of 70 to 400 rpm in a charging step. Image forming device. 41. The conductive magnetic particle carrier according to claim 39, wherein the carrier has a cylindrical shape with an outer diameter of 10 to 20 mm, and rotates at a rotation speed of 140 to 280 rpm in a charging step. Image forming apparatus. 42. The frictional charge amount (Q1) of the toner with the conductive magnetic particles and the frictional charge amount (Q2) of the toner with the magnetic carrier particle particles in the developing device have the following relationship:
<Q2 <Q1 (mC / kg) or 0>Q2> Q1
(MC / kg) is satisfied.
42. The image forming apparatus according to any one of items 41 to 41. 43. The frictional charge (Q1) of the toner with the conductive magnetic particles and the frictional charge (Q2) of the toner with the magnetic carrier particles in the developing device have the following relationship:
≤ | Q1 | ≤60 (mC / kg) and 5≤ | Q2 | ≤60
(MC / kg) is satisfied.
43. The image forming apparatus according to any one of the above items. 44. The developer carrier has an outer diameter of 35 m.
The image forming apparatus according to any one of claims 39 to 43, wherein the image forming apparatus has a cylindrical shape of m or less. 45. The developer carrier has an outer diameter of 10 to 10.
40. A cylindrical shape of 25 mm.
44. The image forming apparatus according to any one of claims 43. 46. The developing device has a developing container for holding the two-component developer, and the amount of the conductive magnetic particles mixed in the developing container is held in the developing container. 20% by weight based on the weight of the magnetic carrier particles used
The image forming apparatus according to any one of claims 39 to 45, wherein: 47. The developing device has a developing container for holding the two-component developer, and the amount of the conductive magnetic particles mixed in the developing container is held in the developing container. 20% by weight based on the weight of the magnetic carrier particles used
The frictional charge (Q1) of the toner with the conductive magnetic particles
And the frictional charge (Q2) of the toner with the magnetic carrier particles in the developing device is expressed by the following relationship: 0 <Q2 <Q1 (mC
The image forming apparatus according to any one of claims 39 to 45, wherein the image forming apparatus satisfies 0 / Q2> Q1 (mC / kg). 48. The developing device has a developing container for holding the two-component developer, and the amount of the conductive magnetic particles mixed in the developing container is held in the developing container. 20% by weight based on the weight of the magnetic carrier particles used
The frictional charge (Q1) of the toner with the conductive magnetic particles
And the triboelectric charge (Q2) between the toner and the magnetic carrier particles in the developing device has the following relationship: 5 ≦ | Q1 | ≦ 60
(MC / kg) and 5 ≦ | Q2 | ≦ 60 (mC / kg)
The image forming apparatus according to any one of claims 39 to 47, wherein the following is satisfied. 49. The conductive magnetic particles for charging may have a particle size of 10 ² to
49. The image forming apparatus according to claim 39, wherein the image forming apparatus has a volume resistivity of ¹⁰ < ¹⁰ > [Omega] .cm. 50. A the charging for the conductive magnetic particles, 10 ⁶ -
49. The image forming apparatus according to claim 39, wherein the image forming apparatus has a volume resistivity of ¹⁰ < ¹⁰ > [Omega] .cm. 51. The conductive magnetic particles for charging are 1 KOe.
The image forming apparatus according to any one of claims 39 to 50, characterized in that it has a 100 emu / cm ³ or more saturated magnetization in a magnetic field of. 52. The conductive magnetic particles for charging are 1 KOe.
The image forming apparatus according to any one of claims 39 to 51 that is characterized in having a saturation magnetization of 150~300emu / cm ³ in a magnetic field of. 53. The conductive magnetic particles for charging are 5 to 80.
53. The image forming apparatus according to claim 39, wherein the image forming apparatus has a volume average particle diameter of μm. 54. The conductive magnetic particles for charging are 10 to 6
The image forming apparatus according to any one of claims 39 to 53, wherein the image forming apparatus has a volume average particle diameter of 0 µm. 55. The conductive magnetic particles for charging have magnetic core particles of resin magnetic particles produced by polymerizing a binder resin, a magnetic metal oxide and a non-magnetic metal oxide. The image forming apparatus according to any one of claims 39 to 54. 56. The method according to claim 39, wherein the voltage applied to the conductive magnetic particle carrier at the time of charging is a DC voltage on which an AC voltage is superimposed. Image forming device. 57. The magnetic carrier particles for development of 10 ⁶
10 The image forming apparatus according to any one of claims 39 to 56, characterized in that it has a volume resistivity of ^{12 Ω} · cm. 58. The magnetic carrier particles for development according to claim 10, wherein
58. The image forming apparatus according to claim 39, having a volume average particle diameter of 60 [mu] m. 59. The magnetic carrier particles for development according to claim 25, wherein
58. The image forming apparatus according to claim 39, having a volume average particle diameter of 60 [mu] m. 60. The magnetic carrier particles for development having a carrier core of resin magnetic particles produced by polymerizing a binder resin, a magnetic metal oxide and a non-magnetic metal oxide. 60. The image forming apparatus according to any one of 39 to 59. 61. The image forming apparatus according to claim 39, wherein the voltage applied to the developer carrier during the development is a DC voltage on which an AC voltage is superimposed. apparatus. 62. The surface of the conductive magnetic particles for charging and the surface of the magnetic carrier particles for development are coated with the same material.
10. The image forming apparatus according to 9. 63. The conductive magnetic particles for charging and the magnetic carrier particles for development are each 10 ⁵ to 10 ¹² Ω · cm.
63. A volume resistivity as defined in claim 62.
An image forming apparatus according to claim 1. 64. The magnetic recording medium according to claim 62, wherein the conductive magnetic particles for charging and the magnetic carrier particles for development both have a volume resistivity of 10 ⁶ to 10 ⁹ Ω · cm. Image forming apparatus. 65. The conductive magnetic particles for charging and the magnetic carrier particles for development are all 50 KOe in a magnetic field of 1 KOe.
65. The image forming apparatus according to claim 62, wherein the image forming apparatus has a magnetization of about 350 emu / cm < ³ >. 66. The conductive magnetic particles for charging and the magnetic carrier particles for development are both 70 μm in a magnetic field of 1 KOe.
65. The image forming apparatus according to claim 62, wherein the image forming apparatus has a magnetization of about 300 emu / cm < ³ >. 67. The magnetic conductive particles for charging and the magnetic carrier particles for developing each have a volume average particle size of 5 to 80 μm.
The image forming apparatus according to any one of the above. 68. The conductive magnetic particles for charging and the magnetic carrier particles for developing each have a volume average particle diameter of 10 to 60 μm.
7. The image forming apparatus according to any one of 6. 69. The conductive magnetic particles for charging have magnetic core particles of resin magnetic particles produced by polymerizing a binder resin, a magnetic metal oxide and a non-magnetic metal oxide. The image forming apparatus according to any one of claims 62 to 68. 70. The method according to claim 62, wherein the voltage applied to the conductive magnetic particle carrier at the time of charging is a DC voltage on which an AC voltage is superimposed. Image forming device. 71. The magnetic carrier particles for development have a carrier core of resin magnetic particles formed by polymerizing a binder resin, a magnetic metal oxide and a non-magnetic metal oxide. The image forming apparatus according to any one of 62 to 70. 72. The image forming apparatus according to claim 62, wherein the voltage applied to the developer carrier during the development is a DC voltage on which an AC voltage is superimposed. apparatus. 73. The image bearing member has a volume resistivity of 10 ⁶ or less.
It has a surface layer of 10 ¹⁴ Ω · cm image forming apparatus according to any one of claims 39 to 72, characterized in. 74. The image bearing member is an organic photoconductor (OP)
74. The image forming apparatus according to claim 39, further comprising: C) a photoconductor. 75. The image forming apparatus according to claim 39, wherein said image carrier has an amorphous silicone (a-Si) photoconductor. 76. The image forming apparatus further includes a transfer device for transferring the toner image formed on the image carrier to a transfer material, and the transfer device includes:
At a position downstream of the transfer device and upstream of the charging device, there is no cleaning device for removing transfer residual toner remaining on the image carrier from the surface of the image carrier. The image forming apparatus according to any one of claims 39 to 75, wherein the transfer residual toner remaining on the image carrier is collected by the developing device.