JP2001235897A - Magnetic toner and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic toner excellent in environmental stability, not causing the scraping of a photoreceptor and the fusion of the toner and stably giving a high-grade image having high resolution even at low humidity over a long period of time and an image forming method. SOLUTION: The average circularity of the magnetic toner is >=0.970, the magnetic toner particles contain at least magnetic iron oxide as a magnetic material and the ratio (B/A) of the amount (B) of elementary iron to the amount (A) of elementary carbon present in the surfaces of the magnetic toner particles measured by the X-ray photoelectron spectroscopic analysis of the magnetic toner is <0.001. The intensity of magnetization of the magnetic toner in a magnetic field of 79.6 kA/m (1,000 Oe) is 10-50 Am2/kg (emu/g), the number average particle diameter of the magnetic material is 0.1-0.3 μm and the number % of particles of <=0.1 μm is <=40%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic toner for use in a recording method such as an electrophotographic method, an electrostatic recording method, a magnetic recording method, and a toner jet method, and an image forming method using the toner.

[0002]

2. Description of the Related Art Conventionally, many proposals have been made regarding magnetic toners and image forming methods.

A method has been proposed in which development is performed using an electrically conductive magnetic toner (US Pat. No. 3,90).
9,258). In this method, a conductive magnetic toner is supported on a cylindrical conductive sleeve having magnetism therein, and is brought into contact with an electrostatic latent image for development. At this time, in the developing unit, a conductive path is formed by the toner particles between the surface of the recording medium and the surface of the sleeve, and electric charges are guided to the toner particles from the sleeve via the conductive path, so that the toner particles are transferred to the image portion of the electrostatic latent image. Due to the Coulomb force, toner particles adhere to the image area and are developed. The developing method using the conductive magnetic toner is an excellent method that avoids the problems associated with the conventional two-component developing method.On the other hand, since the toner is conductive, the developed image can be transferred from a recording medium to plain paper or the like. There is a problem that it is difficult to transfer electrostatically to the final supporting member.

As a developing method using a high-resistance magnetic toner capable of electrostatic transfer, there is a developing method utilizing dielectric polarization of toner particles. However, such a method has a problem that the developing speed is essentially low and the density of a developed image is not sufficiently obtained, and is practically difficult.

As another developing method using a high-resistance insulating magnetic toner, toner particles are frictionally charged by friction between the toner particles, friction between the toner particles and a sleeve, and the like, and this is charged to an electrostatic image holding member. A method of developing by contact is known. However, in this method, the number of times of contact between the toner particles and the friction member is small, and the magnetic toner used has a large amount of magnetic material exposed on the surface of the toner particles. There is such a problem.

Further, a jumping developing method has been proposed (Japanese Patent Laid-Open No. 55-18656, etc.). This involves applying a very thin layer of magnetic toner on a sleeve, triboelectrically charging it, and then developing it in close proximity to the electrostatic image. This method is an excellent method in that the magnetic toner is applied thinly on the sleeve to increase the chance of contact between the sleeve and the toner, thereby enabling sufficient triboelectric charging. However, the developing method using the insulating magnetic toner has an unstable factor related to the insulating magnetic toner to be used. The reason for this is that a considerable amount of fine powdered magnetic material is mixed and dispersed in the insulating magnetic toner, and a part of the magnetic material is exposed on the surface of the toner particles. The characteristics of the magnetic toner are changed, and as a result, various characteristics required for the magnetic toner, such as development characteristics and durability of the magnetic toner, are changed or deteriorated.

[0007] When the conventional magnetic toner containing a magnetic material is used, the above-mentioned problem is considered to be caused mainly by the fact that the magnetic material is exposed on the surface of the magnetic toner. That is, by exposing the magnetic fine particles having relatively lower resistance than the resin constituting the toner on the surface of the magnetic toner, the toner charging performance is reduced, the toner fluidity is reduced, and further, the In use, deterioration of the toner such as a decrease in image density due to the separation of the magnetic material due to friction between the toner or the regulating member and generation of uneven density called a sleeve ghost is caused.

Conventionally, proposals have been made regarding magnetic iron oxide contained in magnetic toners, but they still have points to be improved.

For example, a magnetic toner containing a magnetic iron oxide containing a silicon element has been proposed (Japanese Patent Laid-Open No. Sho 62-62).
279352). Although such a magnetic iron oxide intentionally causes a silicon element to be present inside the magnetic iron oxide, there is still a point to be improved in the fluidity of the magnetic toner containing the magnetic iron oxide.

It has also been proposed to control the shape of magnetic iron oxide to a spherical shape by adding a silicate (Japanese Patent Publication No. 3-9045). In the magnetic iron oxide obtained by this method, a large amount of silicon element is distributed inside the magnetic iron oxide because silicate is used for controlling the particle shape, and the amount of the silicon element on the surface of the magnetic iron oxide is small, The fluidity of the magnetic toner is improved to some extent due to the high smoothness of the magnetic iron oxide, but the adhesion between the binder resin and the magnetic iron oxide constituting the magnetic toner is insufficient.

A method for producing iron sesquioxide by adding a hydrosilosilicate solution during the oxidation reaction to iron sesquioxide has been proposed (JP-A-61-34070). Although triiron tetroxide according to this method has a Si element near the surface, the Si element exists in a layer near the surface of the triiron tetroxide, and the surface is vulnerable to mechanical shock such as friction. Have a point.

On the other hand, the toner is prepared by melt-mixing a binder resin, a colorant, and the like, uniformly dispersing the mixture, pulverizing the mixture with a fine pulverizer, and classifying with a classifier to obtain a toner having a desired particle size. Pulverization method), but there is a limit on the material selection range for reducing the toner particle size. For example, the resin colorant dispersion must be sufficiently brittle and capable of being pulverized with economically available manufacturing equipment. From this request,
In order to make the resin colorant dispersion brittle, when the resin colorant dispersion is actually finely pulverized at a high speed, particles having a wide particle size range are easily formed. Particles) are included in this. Further, such a highly brittle material often undergoes further pulverization or pulverization when used as a developing toner in a copying machine or the like.

In the pulverization method, it is difficult to completely and uniformly disperse solid fine particles such as a magnetic powder or a colorant in a resin, and depending on the degree of the dispersion, an increase in fog and a decrease in image density may occur. Cause. In addition, the grinding method
In essence, the magnetic iron oxide particles are exposed on the surface of the toner, so that there remains a problem in the fluidity of the toner and the charging stability in a severe environment.

That is, in the pulverization method, there is a limit to the fineness of the toner required for high definition and high image quality, and the powder characteristics, particularly the uniform chargeability and fluidity of the toner, are remarkably attenuated.

In order to overcome the problems of the toner by the pulverization method as described above, and to satisfy the above requirements, a method of producing a toner by a suspension polymerization method has been proposed.

Toner by suspension polymerization (hereinafter referred to as “polymerized toner”)
Is easy to make the toner into fine particles, and since the obtained toner is spherical, it has excellent fluidity and is advantageous for high image quality. However, when a magnetic substance is contained in the polymerized toner, its fluidity and charging characteristics are significantly reduced. This is because the magnetic particles are generally hydrophilic and thus easily exist on the toner surface. To solve this problem, it is important to modify the surface characteristics of the magnetic material.

Many proposals have been made regarding surface modification for improving the dispersibility of a magnetic substance in a polymerized toner. For example, various silane coupling agent treatment techniques for magnetic materials have been proposed (JP-A-59-200254, JP-A-59-200256, and JP-A-59-200257).
And JP-A-59-224102), and a technique of treating silicon-containing magnetic particles with a silane coupling agent is also disclosed (JP-A-63-250660, JP-A-10-239897). Gazette).

However, although the dispersibility in the toner is improved to some extent by these treatments, there is a problem that it is difficult to uniformly render the surface of the magnetic material hydrophobic.
Therefore, it is impossible to avoid coalescence of the magnetic substances and generation of magnetic particles that are not hydrophobized, which is insufficient to improve the dispersibility in the toner to a satisfactory level.

As for printer devices, LED and LBP printers have become the mainstream in the recent market, and the direction of technology has been increased to higher resolution, that is, from 240,300 dpi to 400,600,800 dpi. ing. Accordingly, higher definition has been required for the developing system. In addition, the functions of the copying machine have been advanced, and the digital copying machine is moving toward digitalization. In this direction, a method of forming an electrostatic latent image with a laser is mainly used, so that the direction is also moving toward a high resolution direction. Here, as in the case of a printer, a high-resolution and high-definition developing method has been demanded, and a toner having a small particle size has been proposed (Japanese Patent Application Laid-Open No. 1-1112253, 1-191156).
Japanese Patent Application Laid-Open Nos. 2-214156, 2-284158, 3-181952, and 4-162048), but the various problems described above have not been sufficiently solved.

Further, as a toner for developing an electrostatic latent image, a two-component developer composed of a carrier and a toner and a one-component toner (magnetic toner and non-magnetic toner) not requiring a carrier are known. ing. In the two-component system, the toner is charged mainly by friction between the carrier and the toner, and in the one-component system, the toner is charged mainly by the friction between the toner and the charging member.

In addition, regardless of the difference between a two-component system and a one-component system, a method of adding inorganic fine particles as an external additive to toner particles for the purpose of improving the flow characteristics and charging characteristics of the toner and the toner. Has been proposed and widely used.

For example, a method of adding inorganic fine particles which have been subjected to a hydrophobic treatment or inorganic fine particles which have been subjected to a hydrophobic treatment and further treated with a silicone oil or the like (JP-A-5-6660)
No. 8, JP-A-4-98860, etc.) or a method of adding hydrophobically treated inorganic fine particles and silicone oil-treated inorganic fine particles in combination (JP-A-61-249059, JP-A-4-264453, Kaihei 5-346
682) is known.

Also, many methods for adding conductive fine particles as an external additive have been proposed. For example, carbon black as conductive fine particles adheres or adheres to the toner surface for the purpose of imparting conductivity to the toner or for suppressing excessive charging of the toner and making the tribo distribution uniform. It is widely known for use as an external additive. It is also disclosed that conductive fine particles of tin oxide, zinc oxide and titanium oxide are externally added to a high-resistance magnetic toner, respectively (JP-A-57-15195).
No. 2, JP-A-59-168458, JP-A-59-168458,
0-69660).

Also, iron oxide, iron powder,
A toner has been proposed in which conductive magnetic particles such as ferrite are added and the conductive magnetic particles promote charge induction to the magnetic toner to achieve both developability and transferability (Japanese Patent Application Laid-Open No. 56-142540). ). Further, it is disclosed that graphite, magnetite, polypyrrole conductive particles, and polyaniline conductive particles are added to the toner (Japanese Patent Application Laid-Open Nos. 61-275864 and 62-2584).
No. 72, JP-A-61-141452 and JP-A-2-120865), as well as adding various kinds of conductive fine particles to a toner.

On the other hand, as an image forming method, there are conventionally known various methods such as an electrostatic recording method, a magnetic recording method, and a toner jet method. For example, in electrophotography, an electric latent image is generally formed on a photoconductor using a photoconductive substance as an image carrier by various means, and then the electrostatic latent image is developed with toner. After the toner image is transferred to a transfer material such as paper as necessary, the toner image is fixed on a recording medium by heat, pressure or the like to obtain an image.

Various methods are also known for forming a visible image with toner. As a method for visualizing an electrostatic latent image, a cascade developing method, a magnetic brush developing method using a two-component toner composed of a carrier and a toner, a pressure developing method, and the like are known. Further, a magnetic one-component developing method in which a magnetic toner is used and a rotating sleeve having a magnetic pole disposed at the center is used to fly between the photosensitive member and the sleeve by an electric field, and further, the toner carrier is pressed against the image carrier. A contact one-component development method in which toner is transferred by an electric field is also used.

For example, a thin layer of a magnetic developer is applied on a developer carrier, triboelectrically charged, and then brought close to an electrostatic latent image under the action of a magnetic field and opposed without contact, A developing method is disclosed (JP-A-54-43027). According to this method, it is possible to apply sufficient frictional charging of the developer by applying the magnetic developer thinly on the developer carrier, and to develop the developer without contacting the electrostatic latent image while supporting the developer by magnetic force. Is performed, transfer of the developer to the non-image portion, that is, fogging is suppressed, and a high-definition image can be obtained.

Such a one-component developing system does not require carrier particles such as glass beads and iron powder as in the two-component developing system, so that the developing device itself can be reduced in size and weight. Moreover,
In the two-component developing method, since it is necessary to keep the toner concentration in the developer constant, a device for detecting the toner concentration and supplying a necessary amount of toner is required. Therefore, the developing device also becomes large and heavy here. In the one-component developing system, such an apparatus is not required, so that the apparatus can be made small and light, which is preferable.

The toner image formed on the image carrier in the developing step is transferred to a transfer material in the transfer step. In general, however, the toner image is not transferred to the transfer material on the image carrier after the transfer. An image forming method has been used in which the remaining toner is cleaned by various methods, and the above-described process is repeated through a cleaning process of storing the waste toner in a waste toner container. Conventionally, for this cleaning process, blade cleaning, fur brush cleaning, roller cleaning, and the like are used, but all of these methods mechanically scrape off residual toner or dampen and collect the waste toner in a waste toner container. Is what is done. Therefore, there is a problem caused by such a member being pressed against the surface of the image carrier. For example, the image carrier may be worn down by shortening the life by strongly pressing the member.

From the viewpoint of the apparatus, the provision of such a cleaning apparatus inevitably increases the size of the apparatus, which is a bottleneck when the size of the apparatus is reduced. Further, there is a demand for a system with a small amount of waste toner from the viewpoint of resource saving, reduction of waste, and effective utilization of toner.
There is a demand for a toner having good transfer efficiency.

On the other hand, a toner in which the shape factors SF1 and SF2 are specified has been proposed (Japanese Patent Application Laid-Open No. 61-279864).
Gazette). However, this publication has no description about transfer, and as a result of conducting an example, it has been found that the transfer efficiency is low, and further improvement is required.

Further, a magnetic toner which has been made spherical by a mechanical impact force has been proposed (JP-A-63-235953).
No.). However, the transfer efficiency is still inadequate and further improvements are needed.

Further, in order to solve the above problems from another viewpoint, a system free of waste toner and a system excellent in fixing property and offset resistance are desired.

On the other hand, as a system without waste toner, a technique called simultaneous development cleaning or cleanerless has been proposed. However, the disclosure of the conventional technology related to simultaneous cleaning or cleanerless development mainly focuses on a positive memory, a negative memory, and the like due to the influence of the residual toner on the image as disclosed in Japanese Patent Application Laid-Open No. 5-2287. However, as the use of electrophotography is progressing, there is a need to transfer toner images to various transfer materials, and in this sense, it is not satisfactory for various recording media.

Some publications disclose techniques related to cleanerless (Japanese Patent Laid-Open No. 59-1).
No. 33573, JP-A-62-203182,
JP-A-63-133179, JP-A-64-205
No. 87, JP-A-2-302772, JP-A-5
-2289, JP-A-5-53482, JP-A-5-61383, etc.). However, it does not describe a desirable image forming method, nor does it mention the toner composition.

On the other hand, as a development method preferably applied to simultaneous development cleaning or cleaner-less cleaning, conventionally, in simultaneous development cleaning essentially having no cleaning device, a structure in which the surface of an image carrier is rubbed with toner and a toner carrier is used. Because of the necessity, many contact developing methods for contacting the toner or the toner with the image carrier have been studied. This is because it is considered that a configuration in which the toner or the toner comes into contact with and rubs against the image carrier in order to collect the transfer residual toner in the developing unit is considered to be advantageous. However, simultaneous development cleaning or a cleanerless process using the contact development method causes toner deterioration, toner carrier surface deterioration, image carrier surface deterioration or wear due to long-term use, and a sufficient solution to the durability characteristics. Not done. Therefore, a simultaneous development cleaning method using a non-contact development method is desired.

In recent years, from the viewpoint of environmental protection, primary charging and transfer processes using an image carrier contact member have become mainstream instead of conventional primary charging and transfer processes using corona discharge. It is getting.

Conventionally, a corona charger (a corona discharger) is often used as a charging device for uniformly charging (including a charge elimination process) an image carrier to a required polarity and potential.

The corona charger is a non-contact type charging device, which includes a discharge electrode such as a wire electrode and a shield electrode surrounding the discharge electrode, and has a discharge opening facing the image carrier as a member to be charged. The surface of the image carrier is charged in a predetermined manner by exposing the surface of the image carrier to a discharge current (corona shower) generated by applying a high voltage to the discharge electrode and the shield electrode.

In recent years, as a charging device for a member to be charged such as an image carrier, many contact charging devices have been proposed and put into practical use because of their advantages such as low ozone and low power as compared with corona chargers. I have.

The contact charging device includes a charging member such as a roller type (charging roller), a fur brush type, a magnetic brush type, a blade type, or the like. ) Is contacted, and a predetermined charging bias is applied to the contact charging member to charge the surface of the member to be charged to a predetermined polarity and potential.

Contact charging mechanism (charging mechanism,
In the charging principle), two types of charging mechanisms, (1) discharge charging mechanism and (2) direct injection charging mechanism, coexist, and each characteristic appears depending on which is dominant. (1) Discharge Charging Mechanism This mechanism charges the surface of a member to be charged by a discharge phenomenon occurring in a minute gap between the contact charging member and the member to be charged. Since the discharge charging mechanism has a fixed discharge threshold for the contact charging member and the member to be charged, it is necessary to apply a voltage higher than the charging potential to the contact charging member. Further, although the amount of generation is much smaller than that of the corona charger, it is in principle unavoidable to generate a discharge product, so that the harmful effects of active ions such as ozone are inevitable. (2) Direct injection charging mechanism This is a system in which the surface of the object to be charged is charged by injecting charge directly from the contact charging member to the object to be charged. It is also called direct charging, injection charging, or charge injection charging. More specifically, a medium-resistance contact charging member is brought into contact with the surface of the member to be charged, and charges are directly injected into the surface of the member without causing a discharge phenomenon, that is, basically without using discharge. Therefore, even when the voltage applied to the contact charging member is equal to or lower than the discharge threshold, the member to be charged can be charged to a potential corresponding to the applied voltage. Since this charging system does not involve generation of ions, no harm is caused by the discharge products. However, because of direct injection charging, the contact property of the contact charging member to the member to be charged greatly affects the charging property. Therefore, in order to adopt a configuration of contacting the charged object with higher frequency, it is necessary that the contact charging member has a configuration that has a denser contact point, has a large speed difference with the charged object, and the like.

In the contact charging device, a roller charging method using a conductive roller (charging roller) as a contact charging member is preferable from the viewpoint of charging stability, and is widely used.

As the charging mechanism in the conventional roller charging, the discharge charging mechanism (1) is dominant.

The charging roller is made of a conductive or medium-resistance rubber or foam. In some cases, these are laminated to obtain desired characteristics.

The charging roller has elasticity in order to obtain a constant contact state with the member to be charged. However, the charging roller has a large frictional resistance and is often driven by the member to be charged or driven with a slight speed difference. Is done. Therefore, even if the direct injection charging is attempted, the reduction of the absolute charging ability, the lack of the contact property, the uneven contact due to the roller shape, and the uneven charging due to the adhered matter on the charged object are inevitable.

FIG. 7 is a graph showing an example of the charging efficiency of contact charging in electrophotography. The horizontal axis represents the voltage applied to the contact charging member, and the vertical axis represents the charging potential of the member to be charged (hereinafter also referred to as “photoconductor”) obtained at that time. The charging characteristic in the case of roller charging is represented by A. That is, charging starts after passing a discharge threshold of about -500V. Therefore, when charged to -500V, -1000V
Or an AC voltage of 1200 V peak-to-peak so as to always have a potential difference greater than the discharge threshold in addition to a charging bias of -500 V DC to converge the photoconductor potential to the charging potential. The method is general.

More specifically, when a charging roller is pressed against an OPC photosensitive member having a thickness of 25 μm, the surface potential of the photosensitive member increases when a voltage of about 640 V or more is applied. Start, and after that, slope 1 with applied voltage
, The photoconductor surface potential increases linearly. This threshold voltage is defined as a discharge start voltage Vth.

That is, in order to obtain the photosensitive member surface potential (Vd) required for electrophotography, the charging roller needs to have Vd + V
This requires a DC (direct current) voltage larger than required. A method of applying only a DC voltage to the contact charging member to perform charging in this manner is referred to as a “DC charging method”. However, in the DC charging method, since the resistance value of the contact charging member fluctuates due to environmental fluctuations and the like, and Vth fluctuates when the film thickness changes due to shaving of the photoconductor, the potential of the photoconductor is adjusted to a desired value. Difficult to do.

Therefore, in order to further uniform the charging, a voltage obtained by superimposing an AC voltage having a peak-to-peak voltage of 2 × Vth or more on a DC voltage corresponding to a desired Vd is applied to the contact charging member. It has been reported that an "AC charging system" is used (Japanese Patent Laid-Open No. 63-149669). This is for the purpose of effect of leveling the potential by AC, and the potential of the charged body is V V which is the center of the peak of the AC voltage.
It converges to d and is not affected by disturbances such as the environment.

However, even in such a contact charging device, since the essential charging mechanism uses a discharge phenomenon from the contact charging member to the photosensitive member, the charging is applied to the contact charging member as described above. The voltage is required to be higher than the surface potential of the photoreceptor, and a small amount of ozone is generated.

When AC charging is performed for uniform charging, further generation of ozone, generation of vibration noise (AC charging noise) between the contact charging member and the photoreceptor due to the electric field of the AC voltage, and generation of discharge due to discharge. Deterioration of the photoreceptor surface becomes remarkable, and this is a new problem.

On the other hand, in the fur brush charging, a member having a conductive fiber brush portion (fur brush charger) is used as a contact charging member, and the conductive fiber brush portion is brought into contact with a photosensitive member as a member to be charged. The photoreceptor surface is charged to a predetermined polarity and potential by applying a predetermined charging bias. This fur brush charging also has the charging mechanism described in (1) above.
Is dominant.

As the fur brush charger, a fixed type and a roll type are in practical use. A fixed type is obtained by folding a medium-resistance fiber into a base fabric and forming a pile shape and bonding the same to an electrode. The roll type is formed by winding a pile around a cored bar. A fiber density of about 100 fibers / mm ² can be obtained relatively easily, but the contact property is still insufficient to perform sufficiently uniform charging by direct injection charging, and is sufficiently uniform by direct injection charging. To perform charging,
It is necessary to give a speed difference to the photoconductor so as to be difficult as a mechanical configuration, which is not practical.

The charging characteristics of the fur brush charging when a DC voltage is applied are as shown in FIG. 7B. Therefore,
Also in the case of the fur brush charging, in both the fixed type and the roll type, charging is performed by applying a high charging bias and using a discharge phenomenon.

On the other hand, the magnetic brush charging uses a member (magnetic brush charger) having a magnetic brush portion formed as a brush by constraining conductive magnetic particles magnetically with a magnet roll or the like as a contact charging member. The magnetic brush portion is brought into contact with a photosensitive member as a member to be charged, and a predetermined charging bias is applied to charge the surface of the photosensitive member to a predetermined polarity and potential.

In the case of this magnetic brush charging, the charging mechanism is dominated by the direct injection charging mechanism (2). The conductive magnetic particles constituting the magnetic brush portion have a particle size of 5 to 5.
Direct injection charging can be uniformly performed by using a 50 μm-thick one and providing a sufficient speed difference from the photosensitive member.

As shown in C of the charging characteristic graph of FIG.
It is possible to obtain a charging potential substantially proportional to the applied voltage. However, there are also problems such as a complicated device configuration and a problem that the conductive magnetic particles constituting the magnetic brush portion fall off and adhere to the photoreceptor.

The present invention also relates to a contact charging method and a contact transfer method.
The surface of the photoconductor is uniformly charged while applying a voltage to the conductive roller, and then a toner image is obtained by an exposure and development process, and then another conductive roller to which a voltage is applied is pressed against the photoconductor. In the meantime, a method has been disclosed in which a transfer material is passed during this time, a toner image on the photosensitive member is transferred to the transfer material, and a copy image is obtained through a fixing step (Japanese Patent Laid-Open No. 63-149).
669 and JP-A-2-123385. However, the contact charging method or the contact transfer method, unlike the case of using corona discharge, has an alarming problem. Specifically, first, in the case of the contact transfer method, the transfer member is brought into contact with the photoreceptor via the transfer member at the time of transfer, so that the toner image formed on the photoreceptor is transferred to the transfer material. Are pressed against each other, which causes a problem of partial transfer failure called so-called "missing transfer". In addition, as the direction of technology in recent years, a higher resolution and higher definition developing method has been required, and in order to respond to such a demand, the particle diameter of the toner has been reduced, but this has been progressing. As described above, as the toner particle size becomes smaller, the adhesion force (mirror image force, van der Waals force, etc.) of the toner particles to the photoreceptor becomes larger than the Coulomb force applied to the toner particles in the transfer process, and as a result, the transfer residue is reduced. As a result, the amount of toner increases, and the transfer failure tends to be further deteriorated.

On the other hand, in the contact charging method, the charging member is pressed against the surface of the photosensitive member with a pressing pressure. Therefore, when the untransferred residual toner, that is, the transfer residual toner, is pressed against the surface of the photoreceptor, toner abrasion due to abrasion of the surface of the photoreceptor or toner fusing, which is a nucleus generated by the abrasion, easily occurs. It becomes more noticeable as the amount of residual toner increases.

Such abrasion of the photosensitive member and fusion of the toner cause serious defects in forming an electrostatic latent image on the electrostatic image carrier. Specifically, the scraping of the photoreceptor makes primary charging impossible, so the shaved part appears black on the halftone image, and the toner fusion appears white on the halftone image to make latent image formation impossible by exposure. . Further, the transferability of the toner is also deteriorated. Therefore, in combination with the above-described transfer failure, a remarkable image defect appears, and in some cases, the image quality deteriorates synergistically.

Such a problem of abrasion of the photoreceptor and poor transfer is likely to occur when a developer composed of irregular toner particles is used. This is presumably because, in addition to the low transferability of the irregular toner, the edge portion of the toner particles easily scratches the surface of the photoreceptor.

In addition, the problem of abrasion becomes particularly noticeable when a magnetic developer having a magnetic material exposed on the surface of toner particles is used. This is easily understood considering that the exposed magnetic body is directly pressed against the photoconductor.

Further, when the amount of residual toner increases, it becomes difficult to maintain sufficient contact between the contact charging member and the photosensitive member, and the chargeability deteriorates. That is, fogging is likely to occur. This phenomenon is often seen under low humidity where the resistance of the member tends to increase.

As described above, in an image forming method using a contact charging method and a contact transfer method, which are very preferable in consideration of the environment, a magnetic developer which has high transferability and is less likely to cause abrasion of a photoreceptor and toner fusion. The development of is desired.

Next, consider the case where these contact charging methods are applied to the above-mentioned simultaneous cleaning method for development and the cleanerless image forming method.

In the simultaneous development cleaning method and the cleaner-less image forming method, the transfer residual toner remaining on the photosensitive member because it does not have a cleaning member comes into contact with the contact charging member as it is, and adheres or mixes. Further, in the case of a charging method in which a discharge charging mechanism is dominant, the deterioration of the toner due to the discharge energy deteriorates the adhesion to the charging member. If the generally used insulating toner adheres to or mixes with the contact charging member, the charging property is reduced.

In the case of the charging method in which the discharge charging mechanism is dominant, the charging property of the member to be charged decreases sharply from the point where the toner layer adhered to the surface of the contact charging member becomes a resistance inhibiting the discharge voltage. Happens. On the other hand, in the case of the charging method in which the direct injection charging mechanism is dominant, the transfer residual toner adhered or mixed reduces the probability of contact between the surface of the contact charging member and the member to be charged, thereby charging the member to be charged. Is reduced.

The reduction in the uniform chargeability of the charged body causes a decrease in the contrast and the uniformity of the electrostatic latent image after image exposure, and lowers the image density or increases fog.

In the simultaneous development cleaning method and the cleaner-less image forming method, the charge polarity and the charge amount of the transfer residual toner on the photosensitive member are controlled, and the transfer residual toner is stably collected in the developing process. The point is to keep the development characteristics from deteriorating, and the charge polarity and the charge amount of the transfer residual toner are controlled by the charging member.

This will be specifically described using a general laser printer as an example. In the case of reversal development using a charging member to which a negative polarity voltage is applied, a negatively charging photoreceptor, and a negatively charging toner, in the transfer process, the image visualized by the positive polarity transfer member is transferred to a transfer material. But the type of transfer material (thickness,
Depending on the relationship between the image area and the like (difference in resistance, dielectric constant, etc.), the charge polarity of the toner remaining in the transfer varies from plus to minus. However, due to the negative polarity charging member when charging the negatively charged photoreceptor, even the residual toner along with the surface of the photoreceptor uniformly moves to the negative side even if it swings to the positive polarity in the transfer process. The charging polarity can be made uniform. Therefore, when the reversal development is used as the developing method, the negatively charged transfer residual toner remains in the light portion potential portion of the toner to be developed, and the dark portion potential that the toner should not be developed is: Due to the development electric field, the toner is attracted toward the toner carrier, and the transfer residual toner is collected without remaining on the photoconductor having the dark portion potential. That is, by controlling the charging polarity of the toner remaining after transfer at the same time as the charging of the photosensitive member by the charging member, the simultaneous cleaning with development and the cleanerless image forming method are established.

However, if the transfer residual toner adheres to or mixes with the contact charging member beyond the ability to control the toner charging polarity of the contact charging member, the charge polarity of the transfer residual toner cannot be uniformed, and depending on the developing member. It becomes difficult to collect the toner. Even if the toner remaining on the toner carrier is collected by mechanical force such as rubbing, if the charge of the transfer residual toner is not uniform, the chargeability of the toner on the toner carrier is adversely affected, and the developing property is deteriorated. Lower.

That is, in the simultaneous development cleaning and cleanerless image forming method, the charge control characteristic of the transfer residual toner when passing through the charging member and the adhesion / mixing characteristic to the charging member are closely related to the durability characteristic and the image quality characteristic. Is connected to

In order to prevent charging unevenness and perform stable uniform charging, there is disclosed a configuration in which powder is applied to a contact surface of a contact charging member with a surface to be charged (Japanese Patent Publication No. 7-9944).
No. 2). However, the contact charging member (charging roller) is driven to rotate by the member to be charged (photoreceptor) (no speed difference drive), and the generation of ozone products is significantly reduced as compared with a corona charger such as a scorotron. Although,
The charging principle is mainly based on the discharge charging mechanism as in the case of the roller charging described above. In particular, since a voltage obtained by superimposing an AC voltage on a DC voltage is applied in order to obtain more stable charging uniformity, generation of ozone products due to discharge is increased. Therefore, when the apparatus is used for a long time, adverse effects such as image deletion due to ozone products are likely to appear. Further, when the present invention is applied to a cleanerless image forming apparatus, it becomes difficult to uniformly apply the applied powder to the charging member due to mixing of the transfer residual toner, and the effect of performing uniform charging is weakened.

Further, in the image forming method using contact charging, it is possible to prevent toner particles and silica fine particles, which cannot be completely cleaned by blades, from adhering to and accumulating on the surface of the charging means during repeated image formation for a long time. It is disclosed that the toner contains at least visible particles and conductive particles having an average particle size smaller than the visible particles in the toner (JP-A-5-15039). However, the contact charging or the proximity charging used here is based on the discharge charging mechanism, and has the above-described problem due to the discharge charging instead of the direct injection charging mechanism. Further, when applied to a cleaner-less image forming apparatus, compared to a case having a cleaning mechanism, a large amount of conductive fine particles and transfer residual toner have an influence on the chargeability due to passing through a charging process. No consideration is given to the recoverability of the conductive fine particles and the transfer residual toner in the developing process, and the influence of the collected conductive fine particles and the transfer residual toner on the developing characteristics of the toner. Further, when the direct injection charging mechanism is applied to the contact charging, a necessary amount of the conductive fine particles is not supplied to the contact charging member, and a charging failure is caused by the influence of the transfer residual toner.

In the case of proximity charging, it is difficult to uniformly charge the photoreceptor with a large amount of conductive fine particles and transfer residual toner, and the effect of leveling the pattern of the transfer residual toner cannot be obtained. A pattern ghost for blocking image exposure occurs. Further, when the power supply is momentarily interrupted or a paper jam occurs during image formation, contamination inside the apparatus due to toner becomes remarkable.

Further, in the simultaneous cleaning and image forming method for developing, a specific carbon black and a specific azo-based iron may be used to improve the simultaneous cleaning performance by improving the charge control characteristic of the transfer residual toner when passing through the charging member. An image forming method using toner having compound-containing toner particles and inorganic fine particles has been proposed (JP-A-11-15206). Further, in the simultaneous cleaning image forming method, it has been proposed to improve the simultaneous cleaning performance by reducing the residual toner amount by using a toner having an excellent transfer efficiency with a toner shape factor defined. However, the contact charging used here is also based on the discharge charging mechanism, and has the above-mentioned problem due to the discharge charging instead of the direct injection charging mechanism.
Further, these proposals have an effect of suppressing a decrease in chargeability due to transfer residual toner of the contact charging member, but cannot expect an effect of positively increasing chargeability.

Further, some commercially available electrophotographic printers use a roller member which comes into contact with the photoreceptor between the transfer step and the charging step to simultaneously or simultaneously control the recovery of untransferred toner during development. There is also an image forming apparatus. Such an image forming apparatus shows a good cleaning property at the same time as development and can greatly reduce the amount of waste toner.
The cost is increased, and the advantage of simultaneous development and cleaning is impaired in terms of miniaturization. On the other hand, an image forming apparatus in which a toner containing toner particles and conductive charge-promoting particles having a particle size equal to or smaller than 1/2 of the toner particle size is applied to a simultaneous cleaning image forming method using a direct injection charging mechanism. (JP-A-10-307456). According to this proposal, it is possible to obtain a low-cost, compact-size, simultaneous-development-cleaning image forming apparatus capable of significantly reducing the amount of waste toner without generating discharge products, which results in poor charging, light blocking of image exposure, and the like. Alternatively, a good image free from diffusion can be obtained. Also, 1/50 of the toner particle size
An image forming apparatus in which a toner containing conductive particles having a particle size of about 〜 is applied to a simultaneous cleaning image forming method using a direct injection charging mechanism and a conductive particle has a transfer promoting effect is disclosed. (JP-A-10-307421). Further, it has been proposed that the particle size of the conductive fine particles be equal to or smaller than the size of one constituent pixel, and that the particle size of the conductive fine particles be 10 nm to 50 μm in order to obtain better charging uniformity. (JP-A-10-307455).

Further, in order to make it difficult to visually recognize the influence of the defective charging portion on the image in consideration of human visual characteristics, the conductive particles should be about 5 μm or less, preferably 20 nm or less.
It has been proposed that the thickness be 5 μm (JP-A-10-30).
No. 7457).

Further, by setting the particle size of the conductive fine particles to be equal to or smaller than the toner particle size, the development of the toner is hindered during development, or the development bias is prevented from leaking through the conductive fine particles, and the image defect is prevented. By setting the particle size of the conductive fine particles to be larger than 0.1 μm, it is possible to eliminate the problem that the conductive fine particles are embedded in the image carrier and block the exposure, thereby realizing excellent image recording. A simultaneous cleaning image forming method using a charging mechanism has been proposed (JP-A-10-307458).

Conductive fine particles are externally added to the toner, and the conductive fine particles contained in the toner adhere to the image carrier in the developing step at least at the contact portion between the contactable charging member and the image carrier. Further, a development simultaneous cleaning image forming apparatus capable of obtaining a good image which does not cause poor charging, no light blocking of image exposure is obtained by remaining and being carried and interposed on the image carrier even after the transfer step has been disclosed. (Japanese Patent Laid-Open No. Hei 10-30745)
No. 6).

However, these proposals still have room for further improvement in performance when toner particles having a smaller particle size are used in order to enhance stable performance and resolution in repeated use over a long period of time.

As described above, in order to overcome various problems in the magnetic developer and the image forming method using the same, it is necessary to control the exposure of the magnetic substance to the surface of the toner particles. Come. As a specific means, there is surface modification of a magnetic substance, which is as described above. On the other hand, it is known that the particle size distribution of the magnetic powder contributes to the dispersibility of the magnetic material in the toner, but at the present time, there is a proposal that describes the relationship with the exposure of the magnetic material to the toner surface. Absent. Further, as a conventional technique, only a developer in which the particle diameter of a magnetic material is specified has been proposed, and there is still an insufficient point. For example, there has been proposed a developer in which the average particle size and the amount of the magnetic material are defined (Japanese Patent Application Laid-Open No. 5-197187).
However, according to this document, it is described that the charging property, the low-temperature fixing property, and the durability of the developer can be made compatible by using the encapsulated structure. However, in such a developer, there is a concern about the presence of unreacted amino groups remaining at the time of encapsulation, and in consideration of the distribution of the amount of charge, the charge stability remains uneasy.

Further, there has been proposed a developer which defines the average particle diameter of the magnetic material and the shape of the toner suitable for the simultaneous cleaning method (Japanese Patent Laid-Open No. 9-244408). Is not satisfactory with respect to the amount of residual toner after transfer due to the shape.

A proposal has been made on a polymerized capsule toner in which the particle diameter and the amount of the magnetic substance added and the distribution state in the toner particles are specified (Japanese Patent Application Laid-Open No. 7-209904). That is, it has a structure in which a resin layer without magnetic particles is formed in the vicinity of the surface of the toner particles with a thickness of a certain amount or more. It means that it exists. However, in other words, if the average particle diameter of such a developer is as small as 10 μm, for example, the volume in which the magnetic particles can exist is small, and thus it is difficult to include a sufficient amount of the magnetic particles. Moreover, in such a toner, the ratio of the surface resin layer where no magnetic particles are present differs between the toner particles having a large particle diameter and the small particles in the particle size distribution of the toner, and therefore, the content of the magnetic substance included therein is also different. In addition, the developability and transferability also differ depending on the particle size of the developer, and the selective developability depending on the particle size is easily observed. Therefore, when printing with such a magnetic toner for a long period of time, particles that contain a large amount of magnetic material and are difficult to develop,
That is, developer particles having a large particle diameter tend to remain, which leads to a decrease in image density and image quality, and further to a deterioration in fixability.

Further, the average particle size and the particle size distribution of the magnetic material are disclosed, and there are reports that the developing characteristics and the like are satisfactory (Japanese Patent Publication No. 7-82245, Patent 2).
JP-A-756322 / 2759519) is manufactured by a pulverization method, so that there is room for improvement in transferability.

In any case, the particle size distribution of the magnetic material is not described, and there is no magnetic toner that can overcome the above-mentioned problems at the present time.

[0088]

SUMMARY OF THE INVENTION The present invention is to solve the above problems. That is, the object of the present invention is to be less affected by the environment, to have a stable and uniform charging performance, to have no fog, to have a high image density even when used for a long time, to have good transferability, and to have good image reproducibility. To provide an excellent toner and an image forming method.

Another object of the present invention is to provide an image forming method in which the amount of residual toner such as omission during transfer is small and image defects hardly occur even when used for a long time.

It is a further object of the present invention to provide an image forming method capable of stably forming an electrostatic latent image even in a low-humidity environment and having few image defects such as fog due to a decrease in chargeability during durability. It is in.

It is a further object of the present invention to provide an image forming method capable of forming a good cleaning image simultaneously with development.

Another object of the present invention is to provide an image forming method capable of forming a cleaner-less image stably having good chargeability.

[0093]

The present invention relates to a magnetic toner having at least inorganic fine particles on the surface of magnetic toner particles containing at least a binder resin, a wax and a magnetic substance, wherein the magnetic toner has an average circularity of 0%. .970 or more, the magnetic toner particles contain at least magnetic iron oxide as the magnetic substance, and the carbon element present on the surface of the magnetic toner particles measured by X-ray photoelectron spectroscopy of the magnetic toner The ratio (B / A) of the iron element abundance (B) to the abundance (A) is less than 0.001, and the magnetic intensity of the magnetic toner in a magnetic field of 79.6 kA / m (1000 Oersted). Is 10 to 50 Am ² / kg (emu /
g), and the wax has a differential scanning calorimetry (DS)
C) The maximum endothermic peak in the curve is 40 to 120 ° C., the volume average particle diameter of the magnetic substance is 0.1 to 0.3 μm, and the number% of particles of 0.03 to 0.1 μm is 40%.
A magnetic toner characterized by the following.

Also, the present invention provides a charging step of applying a voltage to a charging member to charge an image carrier, an electrostatic latent image forming step of forming an electrostatic latent image on the charged image carrier, A developing step of transferring the toner carried on the toner carrier to the electrostatic latent image formed on the image carrier to form a toner image on the image carrier; and a toner image formed on the image carrier. And an image forming method in which an image is repeatedly formed on an image carrier.In the image forming method, the toner carried on the toner carrier in the developing step is a toner according to the present invention. A magnetic toner, wherein the charging step is a step of charging the image carrier by applying a voltage to a charging member that forms a contact portion with the image carrier and makes contact with the image carrier; Is the way.

[0095]

BEST MODE FOR CARRYING OUT THE INVENTION <1> Raw Material Composition of Magnetic Toner of the Present Invention The magnetic toner of the present invention is a magnetic toner having inorganic fine particles on the surface of magnetic toner particles containing at least a binder resin, a wax and a magnetic substance. It is.

The magnetic material used in the magnetic toner of the present invention has a volume average particle size of 0.1 to 0.3 μm in number-based distribution.
And the number% of particles of 0.03 to 0.1 μm is 4
0% or less.

When an image is obtained from a magnetic toner using a magnetic material having a volume average particle size of less than 0.1 μm, the color of the image shifts to reddish, and the blackness of the image becomes insufficient. It is not generally preferable, for example, the tendency that reddish taste is felt more strongly. In addition, when such a toner is used for a color image, it is not preferable because color reproducibility is hardly obtained and the shape of the color space tends to be distorted. Further, the dispersibility is deteriorated due to the increase in the surface area of the magnetic material, and the energy required for manufacturing increases, which is not efficient. Further, the density of the image to be obtained from the amount of the magnetic substance to be obtained may be insufficient, which is not preferable.

On the other hand, the volume average particle diameter of the magnetic material is 0.3 μm
If the particle size exceeds the limit, the mass per particle increases, so that the probability of exposure to the toner surface due to the difference in specific gravity with the binder during production increases, the possibility of significant wear of the production equipment increases, and the dispersion Is not preferred because the sedimentation stability and the like of the polymer decrease. The magnetic material in the present invention has a volume average particle size of preferably 0.1 to 0.25 μm, and more preferably 0.12 to 0.23 μm.

In the toner, 0.0% of the magnetic material
When the number% of the particles having a particle size of 3 to 0.1 μm exceeds 40%, the surface area of the magnetic material increases, the dispersibility decreases, and agglomerates are easily generated in the toner, and the chargeability of the toner is impaired.
The content is preferably 40% or less in order to increase the possibility that the coloring power is reduced. In particular, 0.03-0.1 μm
Is preferably 1 to 30%, and the number% of particles having a size of 0.3 μm or more is preferably 10% or less.

When the number% of particles of 0.03 to 0.1 μm is 3
When the content is less than 0%, the surface area of the magnetic material increases, the dispersibility decreases, and agglomerates are likely to be formed in the toner, and the tendency to impair the chargeability of the toner and to decrease the coloring power is further reduced. Therefore, it is preferable. In addition, 0.03
Since a magnetic substance having a particle diameter of less than μm receives a small stress during the production of the toner due to a small particle diameter, the probability that the magnetic substance comes to the surface of the toner particles is reduced. Furthermore, even if it is exposed on the particle surface, it hardly acts as a leak site, so that there is substantially no problem. Therefore, in the present invention,
Attention is paid to particles of 0.03 to 0.1 μm, and the number% is defined.

Number% of particles of 0.3 μm or more in magnetic material
Exceeds 10%, the coloring power may be reduced and the image density may be reduced. More preferably, the number% of particles of 0.3 μm or more is 5% or less.

In the present invention, it is preferable to use a magnetic material whose production conditions are set or whose particle size distribution has been adjusted in advance such as pulverization and classification so as to satisfy the above-mentioned particle size distribution conditions. As a classification method, for example, a method using sedimentation separation such as centrifugal separation or a thickener, or a means such as a wet classification device using a cyclone is preferable.

As a method for determining the volume average particle size and the particle size distribution of the magnetic material, for example, a liquid crystal module is attached to a laser diffraction type particle size distribution measuring device (LS-230, manufactured by Coulter Co., Ltd.). A method of measuring in a measurement range, 0.4 with a laser diffraction type particle size distribution measuring device (manufactured by Hiac / Royco: Nicomp Model 370).
A method in which particles of 5 μm or less are measured and determined, or when the magnetic substance itself can be separated, the magnetic substance is embedded in the toner, the toner is embedded in the resin, and then a thin section is formed with a transmission electron microscope (TEM). A method of measuring and determining the particle diameter of 100 magnetic substances in a visual field, and the like can be given. In the present invention, it is preferable to measure with a transmission electron microscope.

As a specific observation method using the TEM described above, the particles to be observed are sufficiently dispersed in an epoxy resin curable at room temperature, and then cured in an atmosphere at a temperature of 40 ° C. for 2 days. A method of observing an object as a flaky sample by a microtome is exemplified. Further, the volume average particle diameter may be calculated by an image analyzer. In the calculation of the volume average particle diameter by the TEM described above, when the particle diameter of the magnetic substance in the visual field is obtained, it may be obtained as a circle equivalent diameter.

[0105] true density of the magnetic material in the magnetic toner of the present invention is a 4.5~5.5g / cm ^3, and bulk density is preferably 0.37~1.00g / cm ^3. In the present invention, the true density of the magnetic material is defined as Micromeritics Acupic 1330 (manufactured by Shimadzu Corporation).
Means the bulk density of the magnetic material, as defined in JIS
(Japanese Industrial Standards) A value measured by K-5101 (1991).

The magnetic material has a true density of 4.5 g / cm.^ThreeNot yet
If it is full, defects may occur inside the magnetic
Tends to be low, and a large amount of crushed material
As a result, the viscosity may increase during dispersion, or
Exposure to the surface may reduce the chargeability
Not preferred. On the other hand, 5.5 g / cm^ThreeBeyond the magnet
The crystallinity of the active substance increases, the hardness increases, and the friction of
Wear tends to be noticeable, or magnetic toner
May not be suitable for electrophotographic processes
Therefore, it is not preferable. A more preferable true density is 4.6 to
5.4 g / cm ^ThreeIt is.

The bulk density of the magnetic material is 0.37 g / cm ³
If it is less than 3, the affinity of the magnetic substance for the dispersion medium is low, so that the viscosity tends to increase during dispersion, and the amount of the dispersion medium must be increased, or the amount of the magnetic substance necessary as a magnetic toner is added. This is not preferable because dispersion conditions such as temperature and dispersion apparatus and dispersion apparatus are extremely limited. The bulk density of the magnetic material is 1.00 g /
If it exceeds cm ³ , the magnetic substance has high agglomeration properties, so that a distribution tends to occur in the dispersed state, and the magnetic distribution of the obtained magnetic toner is also widened, and image fogging and transfer residue increase, which is not preferable.

Further, the bulk density is 0.40 to 0.80 g
/ Cm ³ is more preferable because the above-mentioned problems are further reduced. One example of controlling the true density and the bulk density of the magnetic material in the present invention to the above ranges includes controlling the shape, particle size distribution, and surface characteristics of the magnetic material.

In the present invention, as the magnetic substance to be contained in the toner particles in order to make the toner into a magnetic toner, specifically, a magnetic iron oxide such as magnetite, maghematite, ferrite, a metal such as iron, cobalt, nickel or the like; Metals and aluminum, cobalt, copper, lead, magnesium, tin, zinc, antimony, beryllium, bismuth,
Cadmium, calcium, manganese, selenium, titanium,
Examples include alloys of metals such as tungsten and vanadium and mixtures thereof, which contain at least magnetic iron oxide.

Examples of such a magnetic substance include triiron tetroxide which may contain elements such as phosphorus, cobalt, nickel, copper, magnesium, manganese, aluminum, and silicon;
Examples thereof include those mainly containing iron oxide such as iron oxide, and these are used alone or in combination of two or more. Among such magnetic materials, those mainly containing triiron tetroxide are particularly preferable.

These magnetic materials have a Mohs hardness of 5 to 5.
7 are preferred.

The shape of the magnetic material is octahedron, hexahedron,
There are spheres, needles, scaly shapes and the like, but octahedrons, hexahedrons, spheres, irregular shapes and the like with little anisotropy are preferred for increasing the image density. The shape of such a magnetic body can be confirmed by SEM or the like.

The magnetic properties of the magnetic material include a magnetic field of 795.
8 kA / m or less, saturation magnetization is 10 to 200 Am ² / k
g, residual magnetization is 1 to 100 Am ² / kg, coercive force is 1 to
Those having 30 kA / m are preferably used.

In the present invention, the magnetic properties of the magnetic material can be measured at room temperature of 25 ° C. and an external magnetic field of 796 kA / m using a vibrating magnetometer VSMP-1-10 (manufactured by Toei Industry Co., Ltd.).

In the present invention, it is preferable that the magnetic material is subjected to a surface treatment using a coupling agent in an aqueous medium, so that the particle surface of the magnetic material is made hydrophobic. When hydrophobizing the surface of a magnetic material, a method of performing a surface treatment while hydrolyzing with a coupling agent while dispersing magnetic particles to a primary particle size in an aqueous medium is used. Rather than treating in the gas phase,
The magnetic particles are less likely to coalesce, and a repelling action between the magnetic particles due to the hydrophobic treatment acts, so that the magnetic material is surface-treated in a substantially primary particle state.

The method of treating the surface of a magnetic substance with a coupling agent in an aqueous medium does not require the use of a coupling agent that generates a gas, such as chlorosilanes or silazanes, and furthermore, a gaseous phase. Among them, magnetic particles are easily united with each other, and a high-viscosity coupling agent, which has been difficult to treat well, can be used, and the effect of hydrophobization is enormous.

Examples of the coupling agent that can be used in the surface treatment of the magnetic material in the present invention include a silane coupling agent and a titanium coupling agent.
More preferably used is a silane coupling agent, which is represented by the general formula (I).

[0118]

## STR1 R _m SiY _n (I) [wherein, R represents an alkoxy group, m represents an integer of 1 to 3, Y is an alkyl group, vinyl group, glycidoxy group, hydrocarbon group such as methacrylic group And n represents an integer of 1 to 3. However, m + n = 4. Examples of the silane coupling agent represented by the general formula (I) include vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, methyltrimethoxysilane, and methyltriethoxy. Silane, isobutyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane,
Examples include hydroxypropyltrimethoxysilane, phenyltrimethoxysilane, n-hexadecyltrimethoxysilane, and n-octadecyltrimethoxysilane.

In particular, it is preferable to subject the magnetic particles to a hydrophobic treatment in an aqueous medium using an alkyl trialkoxysilane coupling agent represented by the general formula (II).

[0120]

Embedded image in _{C p H 2p + 1 -Si- (} OC q H 2q + 1) 3 (II) [ wherein, p represents an integer of 2 to 20, q is an integer of 1-3. When p in the above formula is smaller than 2, the hydrophobic treatment becomes easy, but it is difficult to impart sufficient hydrophobicity, and it becomes difficult to suppress the exposure of the magnetic particles from the toner particles. On the other hand, when p is larger than 20, the hydrophobicity is sufficient, but the coalescence of the magnetic particles increases, and it becomes difficult to sufficiently disperse the magnetic particles in the toner, and fog and transferability are deteriorated. It tends to worsen. On the other hand, when q is larger than 3, the reactivity of the silane coupling agent decreases, and it becomes difficult to sufficiently perform the hydrophobic treatment.

From the above, p in the formula represents an integer of 2 to 20, more preferably an integer of 3 to 15, and q represents 1 to 3.
It is preferable to use an alkyltrialkoxysilane coupling agent having an integer of 1 or 2, more preferably 1 or 2.

The amount of the treatment is preferably 0.05 to 20 parts by mass, more preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the magnetic material.

In the present invention, the aqueous medium is a medium containing water as a main component. Specifically, water-based media include water itself, water with a small amount of a surfactant added, water with a pH adjuster, and water with an organic solvent. As the surfactant, a nonionic surfactant such as polyvinyl alcohol is preferable. The surfactant is preferably added in an amount of 0.1 to 5% by mass relative to water. pH adjusters include inorganic acids such as hydrochloric acid. Examples of the organic solvent include methanol and the like.
The organic solvent is preferably added in an amount of 0 to 500% by mass based on water.

In order to treat a magnetic substance with a coupling agent in an aqueous medium as a surface treatment, a method in which an appropriate amount of a magnetic substance and a coupling agent are stirred in an aqueous medium can be mentioned. For example, using a mixer having a stirring blade (specifically, a high shear mixing device such as an attritor or a TK homomixer)
It is preferred that the magnetic particles be sufficiently converted into primary particles in an aqueous medium.

In the thus obtained magnetic material whose surface has been treated, no aggregation of particles is observed and the surface of each particle is uniformly subjected to hydrophobic treatment. Very good dispersibility in. Moreover, there is no exposure from the surface of the toner particles, and a polymer toner having a substantially spherical shape can be obtained.

The magnetic material used in the magnetic toner of the present invention is, for example, magnetite manufactured by the following method.

An aqueous solution containing ferrous hydroxide is prepared by adding an equivalent such as sodium hydroxide to the iron component aqueous solution in an amount equivalent to or more than the equivalent of the iron component. Air is blown in while maintaining the pH of the prepared aqueous solution at pH 7 or more (preferably pH 8 to 10), and while the aqueous solution is heated to 70 ° C. or more, the oxidation reaction of ferrous hydroxide is carried out. First, a seed crystal is produced.

Next, an aqueous solution containing about 1 equivalent of ferrous sulfate based on the amount of the alkali previously added is added to the slurry-like liquid containing the seed crystals. The reaction of ferrous hydroxide is promoted while blowing air while maintaining the pH of the solution at 6 to 10 to grow magnetic iron oxide particles with the seed crystal as a core. As the oxidation reaction proceeds, the pH of the solution shifts to the acidic side,
It is preferable that the pH of the liquid is not less than 6. At the end of the oxidation reaction, adjust the pH of the solution, stir well so that the magnetic iron oxide becomes primary particles, add the coupling agent, mix and stir well, then stir, filter, dry and lightly disintegrate By doing so, hydrophobically treated magnetic iron oxide particles are obtained. Alternatively, after the oxidation reaction is completed, the iron oxide particles obtained by washing and filtration are re-dispersed in another aqueous medium without drying, and then the pH of the re-dispersed liquid is adjusted. A coupling treatment may be performed by adding a coupling agent. In any case, it is important to perform a surface treatment after the oxidation reaction without going through a drying step, which is an important point in the magnetic toner and the image forming method of the present invention.

As the ferrous salt, generally, iron sulfate produced as a by-product in the production of titanium sulfate and iron sulfate produced as a by-product of cleaning the surface of a steel sheet can be used. Further, iron chloride and the like can be used. is there.

A method for producing magnetic iron oxide by an aqueous solution method is as follows.
Generally, an iron concentration of 0.5 to 2 mol / l is used from the viewpoint of preventing the viscosity from increasing during the reaction and the solubility of iron sulfate. Generally, the lower the concentration of iron sulfate, the smaller the particle size of the product tends to be. In addition, in the reaction, as the amount of air is larger and the reaction temperature is lower, the particles are easily atomized.

By using the magnetic toner made of the hydrophobic magnetic particles produced as described above, high quality and high stability can be achieved without causing abrasion of the photoreceptor and toner fusion. .

The magnetic material used in the magnetic toner used in the present invention is 10 to 2 parts by mass based on 100 parts by mass of the binder resin.
It is preferable to use 00 parts by mass. It is more preferable to use 20 to 180 parts by mass. If the amount is less than 10 parts by mass, the coloring power of the magnetic toner is poor, and it may be difficult to suppress fog. On the other hand, if it exceeds 200 parts by mass,
In some cases, the holding force due to the magnetic force on the toner carrier is increased and the developing property is reduced, and not only is it difficult to uniformly disperse the magnetic substance into individual toner particles, but also the fixing property is reduced.

As the binder resin used in the magnetic toner of the present invention, when the magnetic toner is produced by a pulverization method, there may be mentioned a resin used as a binder resin as it is. For example, homopolymers of styrene such as polystyrene and polyvinyltoluene and substituted products thereof; styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-
Vinyl naphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-dimethylaminoethyl acrylate Polymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-dimethylaminoethyl methacrylate copolymer, styrene-vinyl methyl ether copolymer Polymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer Styrene-based copolymers such as Methyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyethylene, polypropylene, polyvinyl butyral, silicone resin,
Polyester resin, polyamide resin, epoxy resin, polyacrylic acid resin, rosin, modified rosin, temper resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, paraffin wax, carnauba wax, etc. alone or Can be mixed and used. In particular,
Styrene copolymer and polyester resin have development characteristics,
It is preferable in terms of fixability and the like.

The glass transition temperature (Tg) of the binder resin is as follows:
The temperature is preferably from 50 to 70 ° C., and if it is lower than 50 ° C., the storage stability of the toner is reduced, and if it is higher than 70 ° C., the fixability is poor.

The glass transition temperature (Tg) of the binder resin can be measured in the same manner as the maximum endothermic peak in a differential scanning calorimetry (DSC) curve of wax described later. That is, the glass transition temperature (Tg) is measured according to “ASTMD3418-8” using DSC-7 manufactured by PerkinElmer. The temperature correction of the device detection unit uses the melting points of indium and zinc, and the heat quantity correction uses the heat of fusion of indium. The measurement can be performed by using an aluminum pan as a measurement sample, setting an empty pan as a control, and performing the measurement at a heating rate of 10 ° C./min.

In the case where the magnetic toner of the present invention is obtained by a polymerization method, a polymerizable monomer which can be a binder resin can be mentioned. Examples of the polymerizable monomer include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, and p-methylstyrene.
-Methoxystyrene, styrene monomers such as p-ethylstyrene, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, n-propyl acrylate, n-octyl acrylate, dodecyl acrylate, Acrylates such as 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate;
Methacrylates such as n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate and the like Other monomers such as acrylonitrile, methacrylonitrile, and acrylamide are exemplified.

These monomers can be used alone or as a mixture. Among the above-mentioned monomers, it is preferable to use styrene or a styrene derivative alone or in combination with another monomer from the viewpoint of the developing characteristics and durability of the toner.

The magnetic toner of the present invention has inorganic fine particles on the surface of at least the magnetic toner particles comprising the binder resin and the magnetic material.

The inorganic fine particles are added to improve the fluidity of the magnetic toner and to make the toner particles uniform in charge. However, the inorganic fine particles are subjected to a treatment such as hydrophobic treatment to adjust the charge amount of the toner and to improve environmental stability. It is also a preferable embodiment to provide functions such as improvement.

The inorganic fine particles as a fluidizing agent preferably have a number average primary particle size of 4 to 80 nm.

The number average primary particle size of the inorganic fine particles is 80 nm.
When the toner particles are larger than the above, or when no inorganic fine particles having a size of 80 nm or less are added, the transfer residual toner easily adheres to the charging member when it adheres to the charging member, and it is possible to stably obtain good charging characteristics. It can be difficult. Also,
Good toner fluidity cannot be obtained, and the charging of toner particles tends to be non-uniform, and problems such as an increase in fog, a decrease in image density, and toner scattering may not be avoided. When the number average primary particle size of the inorganic fine particles is smaller than 4 nm, the cohesiveness of the inorganic fine particles is increased, and the inorganic fine particles behave not as primary particles but as agglomerates having a wide particle size distribution with strong cohesiveness that is difficult to be broken even by a crushing treatment. Therefore, image defects such as development of aggregates and damage to the image carrier or the development carrier are likely to occur. In order to make the charge distribution of the toner particles more uniform, the number average primary particle size of the inorganic fine particles is 6 to 35 n.
m is more preferable.

In the present invention, the method of measuring the number average primary particle diameter of the inorganic fine particles is based on a photograph of the toner magnified by a scanning electron microscope, and further by an elemental analysis means such as XMA attached to the scanning electron microscope. While contrasting the toner image mapped with the element contained in the fine particles,
It can be obtained by measuring 100 or more primary particles of the inorganic fine particles adhering to or free from the surface of the toner particles and calculating the number average particle diameter.

As the inorganic fine particles used in the present invention,
Inorganic fine particles selected from silica, alumina, and titania, or double oxides thereof can be used.

Examples of the double oxide of silica include fine silica powder.

As the silicic acid fine powder, both a so-called dry method produced by the vapor phase oxidation of a silicon halide or a so-called fumed silica, and a so-called wet silica produced from water glass or the like are used. Although it is possible, dry silica having less silanol groups on the surface and in the inside of the fine silicic acid powder and less production residue such as Na ₂ O and SO ₃ ^2- is preferred. In the case of fumed silica, it is also possible to obtain a composite fine powder of silica and another metal oxide by using another metal halide such as aluminum chloride and titanium chloride together with a silicon halide in the production process. Is also included.

The addition amount of the inorganic fine particles having a number average primary particle size of 4 to 80 nm is preferably 0.1 to 3.0% by mass based on the toner particles, and if the addition amount is less than 0.1% by mass. The effect is not sufficient, and when the content is 3.0% by mass or more, the fixing property may be deteriorated.

The inorganic fine particles in the present invention are preferably inorganic fine particles which have been subjected to a hydrophobic treatment from the viewpoint of electrophotographic properties under a high temperature and high humidity environment. When the inorganic fine particles added to the toner absorb moisture, the charge amount of the toner particles is significantly reduced, and the toner is easily scattered.

Examples of the hydrophobizing agent for hydrophobizing inorganic fine particles include silicone varnish, various modified silicone varnishes, silicone oil, various modified silicone oils, silane compounds, silane coupling agents, and other organosilicon compounds and organotitanium compounds. Such treating agents may be used, and may be used alone or in combination.

Among them, those treated with silicone oil are preferred, and more preferably, those treated with silicone oil at the same time as or after treating the inorganic fine particles with the above-mentioned hydrophobizing agent are used for the magnetic toner particles. This is good for keeping the charge amount of the toner particles high even under a high humidity environment and preventing toner scattering.

The conditions for treating such inorganic fine particles include, for example, as a first-stage reaction, a silylation reaction is carried out with the above-mentioned hydrophobizing agent, a silanol group is eliminated by a chemical bond, and a hydrophobic treatment is carried out. As a result, a hydrophobic thin film can be formed on the surface with silicone oil, and the hydrophobicity can be further increased. A more preferred treatment method is a method in which a silane compound is used as a hydrophobizing agent in the first-stage reaction, and treatment is performed with silicone oil in the second-stage reaction.

As a method of treating silicone oil, specifically, for example, inorganic fine particles treated with a silane compound and silicone oil may be directly mixed using a mixer such as a Henschel mixer, or silicone fine particles may be added to inorganic fine particles. A method of spraying oil may be used. Alternatively, a method of dissolving or dispersing silicone oil in an appropriate solvent, adding inorganic fine particles, mixing and removing the solvent may be used. A method using a sprayer is more preferable because the formation of aggregates of inorganic fine particles is relatively small.

The silicone oil has a viscosity at 25 ° C. of 10 to 200,000 mm ² / s, more preferably 3,000 to 80,000 mm ² / s. If it is less than 10 mm ² / s, the inorganic fine particles have no stability and the image quality tends to deteriorate due to heat and mechanical stress. If it exceeds 200,000 mm ² / s,
Uniform processing tends to be difficult.

As such a silicone oil, for example, dimethyl silicone oil, methylphenyl silicone oil, α-methylstyrene modified silicone oil, chlorophenyl silicone oil, fluorine modified silicone oil and the like are particularly preferable.

The processing amount of the silicone oil is 1 to 23 parts by mass, preferably 5 to 2 parts by mass, per 100 parts by mass of the inorganic fine particles.
0 parts by mass is good. If the amount of the silicone oil is too small, good hydrophobicity cannot be obtained, and if the amount is too large, problems such as fogging may occur.

Examples of the silane compound for treating the inorganic fine particles include an organic silicon compound such as hexamethyldisilazane.

The inorganic fine particles used in the present invention are BET.
Specific surface area is 20 ~ 250m by nitrogen adsorption measured by the method
² / g is preferable, and more preferably 40 to
Those with 200 m ² / g are even better.

The specific surface area is determined by adsorbing nitrogen gas on the sample surface using a specific surface area measuring device Autosorb 1 (manufactured by Yuasa Ionics) according to the BET method and calculating the specific surface area using the BET multipoint method. Obtainable.

The magnetic toner of the present invention contains a wax, and the maximum endothermic peak of the wax in a differential scanning calorimetry (DSC) curve is in the range of 40 to 120 ° C.
The reason is that, in the present invention, a magnetic substance and a wax having a maximum endothermic peak in the above-mentioned temperature range are contained as essential components, and when toner particles are produced in the presence of both, the electronic properties of the obtained toner are reduced. This is because environmental stability in photographic characteristics is enhanced. Although the mechanism of such development cannot be determined at this time, due to the low surface tension characteristic of wax compounds, the wax compound forms a thin film on the surface of the magnetic material inside the toner particles during the production of toner particles, and charges from the magnetic material. It is thought that it is suppressing that the leak. However, if the maximum endothermic peak is less than 40 ° C., the wax tends to bleed out to the surface of the toner particles, and the probability that the toner is fused to the surface of the photoreceptor becomes extremely high, so that the adverse effect is stronger than the above effect. Not preferred. Further, a wax having a maximum endothermic peak exceeding 120 ° C. has an undesirably high melting point, so that it is difficult to form a thin film on the surface of the magnetic substance during the production of toner particles, and it is difficult to obtain the above-mentioned effects.

The above-described effects are more preferable when combined with a surface-modified magnetic material because a further synergistic effect is exhibited.

The wax component was measured by differential scanning calorimetry (DS).
C) The maximum endothermic peak in the curve is preferably in the range of 40 to 110 ° C, more preferably in the range of 45 to 90 ° C.

By having the maximum endothermic peak in the above-mentioned temperature range, it greatly contributes to low-temperature fixing, and also effectively develops releasability. If the maximum endothermic peak is less than 40 ° C., the self-cohesive force of the wax component becomes weak, and as a result, the high-temperature offset resistance may deteriorate. On the other hand, if the maximum endothermic peak exceeds 110 ° C., the fixing temperature becomes high, and low-temperature offset tends to occur, which is not preferable. Further, when the toner is directly obtained by a polymerization method by performing granulation / polymerization in an aqueous medium, if the maximum endothermic peak temperature is high, a problem such as precipitation of a wax component mainly during granulation may occur, which is not preferable. .

Differential scanning calorimetry (DS) of the wax component
C) The measurement of the maximum endothermic peak temperature in the curve is performed by the method of “AS
TMD 3418-8 ". For the measurement, for example, DSC-7 manufactured by PerkinElmer is used. The temperature correction of the device detection unit uses the melting points of indium and zinc, and the heat quantity correction uses the heat of fusion of indium. An aluminum pan is used as a measurement sample, an empty pan is set as a control, and the measurement is performed at a heating rate of 10 ° C./min.

The magnetic toner according to the present invention preferably contains a wax as a release agent in an amount of 0.1 to 20% by mass based on the whole magnetic toner.
Thereafter, the toner image transferred onto the transfer material is fixed on the transfer material by energy such as heat and pressure, and a semi-permanent image is obtained. At this time, a hot roll type fixing is generally often used. As will be described later, an extremely high-definition image can be obtained by using a magnetic toner having a weight average particle diameter of 10 μm or less. The fibers enter the gaps between the fibers and receive insufficient heat from the heat fixing roller, so that low-temperature offset is likely to occur. However, by incorporating an appropriate amount of wax as a release agent in the magnetic toner of the present invention, it becomes possible to prevent shaving of the photoreceptor while achieving both high resolution and offset resistance. A more preferable content of the wax is 0.5 to the entire magnetic toner.
１８18% by mass.

Examples of the wax usable in the magnetic toner of the present invention include petroleum waxes such as paraffin wax, microcrystalline wax and petrolactam and derivatives thereof, montan wax and derivatives thereof, and hydrocarbon waxes and derivatives thereof by the Fischer-Tropsch method.
Examples include polyolefin wax represented by polyethylene and its derivatives, natural wax such as carnauba wax and candelilla wax, and its derivatives. The derivatives include oxides, block copolymers with vinyl monomers, and graft-modified products. Furthermore, fatty acids such as higher aliphatic alcohols, stearic acid and palmitic acid, or compounds thereof, acid amide waxes, ester waxes, ketones, hydrogenated castor oil and derivatives thereof, vegetable waxes, animal waxes and the like can also be used.

The content of these wax components in the magnetic toner of the present invention is preferably in the range of 0.1 to 20% by mass based on the whole magnetic toner, but the content is preferably 0.1 to 20% by mass.
If the amount is less than 1% by mass, the low-temperature offset suppressing effect is poor, and 2
If the amount exceeds 0% by mass, the long-term storability deteriorates, the dispersibility of other toner materials deteriorates, and the fluidity of the toner deteriorates and the image characteristics may deteriorate.

The magnetic toner of the present invention may contain a charge control agent for stabilizing the charge characteristics. As the charge control agent, a known charge control agent can be used. In particular, a charge control agent having a high charging speed and capable of stably maintaining a constant charge amount is preferable. Further, when the magnetic toner is produced by a direct polymerization method, a charge control agent having a low polymerization inhibitory property and having substantially no solubilized substance in an aqueous dispersion medium is particularly preferable.

Specific examples of the charge control agent include metal compounds of aromatic carboxylic acids such as salicylic acid, alkylsalicylic acid, dialkylsalicylic acid, naphthoic acid and dicarboxylic acid, and metal salts of azo dyes or azo pigments as negative charge control agents. Alternatively, a metal complex, a high molecular compound having a sulfonic acid or carboxylic acid group in a side chain, a boron compound, a urea compound, a silicon compound, calixarene, and the like can be given.

Examples of the positive charge control agent include a quaternary ammonium salt, a polymer compound having the quaternary ammonium salt in the side chain, a guanidine compound, a nigrosine compound, and an imidazole compound.

The charge control agent is preferably used in an amount of 0.5 to 10 parts by mass based on 100 parts by mass of the binder resin. However, in the magnetic toner of the present invention, the addition of a charge control agent is not essential, and the charge control agent is not necessarily included in the magnetic toner by positively utilizing frictional charging between the layer pressure regulating member of the magnetic toner and the toner carrier. Need not be included.

It is preferable that the conductive fine particles contained in the magnetic toner of the present invention have a volume average particle diameter smaller than the weight average particle diameter of the magnetic toner. Although the weight average particle size and the volume average particle size are not compared on the same scale, since the conductive fine particles are relatively smaller than the magnetic toner,
In the present invention, these are used as one index for comparing the sizes of the magnetic toner and the conductive fine particles.

The volume average particle diameter of the conductive fine particles is 0.5 μm
It is more preferable to use the above. If the volume average particle diameter of the conductive fine particles is small, the content of the conductive fine particles in the whole toner must be set small in order to prevent a decrease in the developing property. If the volume average particle size of the conductive fine particles is less than 0.5 μm, an effective amount of the conductive fine particles cannot be secured, and in the charging step, charging is hindered due to adhesion and mixing of the insulative transfer residual toner to the contact charging member. A sufficient amount of conductive fine particles for overcoming and charging the image carrier satisfactorily can not be interposed in the contact portion between the charging member and the image carrier or in the charged area in the vicinity thereof, which causes poor charging. It is easy to occur. From this viewpoint, the volume average particle diameter of the conductive fine particles is preferably 0.8 μm or more, and more preferably 1.
1 μm or more is good.

When the volume average particle size of the conductive fine particles is larger than the weight average particle size of the magnetic toner particles, the conductive fine particles are easily released from the toner particles when mixed with the toner. The supply amount is insufficient, and it is difficult to obtain sufficient chargeability. Further, the conductive fine particles dropped from the charging member may shield or diffuse the exposure for writing the electrostatic latent image, thereby causing a defect of the electrostatic latent image and deteriorating the image quality. Furthermore, when the volume average particle diameter of the conductive fine particles is large,
Since the number of particles per unit mass is reduced, the conductive fine particles are transferred to the contact area between the charging member and the image carrier or in the vicinity of the charging area in consideration of the reduction or deterioration due to the dropping of the conductive fine particles from the charging member. In order for the conductive fine particles to be continuously supplied and interposed one after another, and for the contact charging member to maintain the dense contact with the image carrier via the conductive fine particles and to stably obtain good chargeability. However, the content of the conductive fine particles in the entire toner must be increased. However, if the content of the conductive fine particles is too large, the chargeability and developability of the toner as a whole, particularly in a high-humidity environment, tend to decrease, resulting in a decrease in image density and toner scattering. From such a viewpoint, the volume average particle diameter of the conductive fine particles is preferably 3
μm or less is good.

In the present invention, the content of the conductive fine particles in the whole magnetic toner is preferably 0.2 to 10% by mass. The magnetic toner of the present invention has a high charge amount because the magnetic substance is not substantially exposed on the surface, and if the content of the conductive fine particles with respect to the entire magnetic toner is less than 0.2% by mass, the developability is deteriorated. Tend to. Also, 0.2
When the amount is less than 10% by mass, when applied to an image forming method using simultaneous development and cleaning, the charging of the image carrier is overcome by overcoming the charging inhibition due to the adhesion and mixing of the insulating transfer residual toner to the contact charging member. A sufficient amount of conductive fine particles for good performance cannot be interposed in the contact area between the charging member and the image carrier or in the vicinity of the charged area, resulting in poor charging performance and poor charging. There is.

When the content is more than 10% by mass, the chargeability and developability of the toner in the developing section are reduced due to the excessive amount of the conductive fine particles recovered by the simultaneous cleaning for development, and the image density is reduced. This causes a drop and toner scattering. The content of the conductive fine particles with respect to the entire magnetic toner is more preferably 0.5 to 5% by mass.

The resistance of the conductive fine particles is 1 × 10 ⁹
It is preferably Ω · cm or less. If the resistance of the conductive fine particles is greater than 1 × 10 ⁹ Ω · cm, the developability tends to decrease, and the conductive fine particles are charged when applied to an image forming method using simultaneous cleaning with development. Good chargeability even when the contact portion between the member and the image carrier is interposed in or near the charging area to maintain the dense contact with the image carrier through the conductive fine particles of the contact charging member. In some cases, the effect of accelerating the charge for obtaining the toner may not be obtained.

In order to sufficiently draw out the effect of accelerating the electrification of the conductive fine particles and stably obtain good chargeability, the resistance of the conductive fine particles is limited by the resistance of the surface of the contact charging member or the contact with the image carrier. It is preferably smaller than the resistance. Further, when the resistance of the conductive fine particles is 1 × 10 ⁶ Ω · cm or less, the charging of the image carrier is overcome by overcoming the charging inhibition due to the adhesion and mixing of the insulating transfer residual toner to the contact charging member. It is more preferable for better performance. Particularly preferred resistance of the conductive fine particles is 1 × 10 ⁻¹ to 1 × 10 ⁶ Ω · cm.
It is.

The conductive fine particles are preferably transparent, white or light-colored conductive fine particles, because the conductive fine particles transferred onto the transfer material are not conspicuous as fog. The conductive fine particles are preferably transparent, white or light-colored conductive fine particles even in the sense that they do not hinder the exposure in the electrostatic latent image forming step, and more preferably, the conductive fine particles have a transmittance of 30% to exposure light. It is better to be above.

In the present invention, the light transmittance of the conductive fine particles can be measured according to the following procedure. The transmittance is measured in a state where one layer of the conductive fine particles is fixed on a transparent film having an adhesive layer on one side. The light is irradiated from the vertical direction of the sheet, and the light transmitted to the back of the film is collected and the amount of light is measured. The transmittance of the conductive fine particles is calculated as a net light amount from the light amount when only the film and the conductive fine particles are adhered. Specifically, X-Rite 310T
It can be measured using a transmission densitometer.

The conductive fine particles of the present invention are preferably non-magnetic, and include, for example, fine carbon powder such as carbon black and graphite; fine metal powder such as copper, gold, silver, aluminum and nickel; Metal oxides such as titanium oxide, tin oxide, aluminum oxide, indium oxide, silicon oxide, magnesium oxide, barium oxide, molybdenum oxide, iron oxide, and tungsten oxide; metal compounds such as molybdenum sulfide, cadmium sulfide, and potassium titanate; or These composite oxides can be used by adjusting the particle size and particle size distribution as needed. Among these, conductive inorganic oxide fine particles such as zinc oxide, tin oxide, and titanium oxide are particularly preferable.

For the purpose of controlling the resistance value of the conductive inorganic oxide, inorganic oxide fine particles having a conductive material such as a metal oxide doped with an element such as antimony or aluminum on the surface can be used. . Specific examples include titanium oxide fine particles surface-treated with tin oxide / antimony, stannic oxide fine particles doped with antimony, and stannic oxide fine particles.

Examples of commercially available conductive titanium oxide fine particles surface-treated with tin oxide / antimony include, for example, EC-3.
00 (Titanium Industry Co., Ltd.), ET-300, HJ-
1, HI-2 (above, Ishihara Sangyo Co., Ltd.), WP (Mitsubishi Materials Corporation) and the like.

Commercially available antimony-doped conductive tin oxide includes, for example, T-1 (Mitsubishi Materials Corporation) and SN-100P (Ishihara Sangyo Co., Ltd.), and commercially available stannic oxide includes SH. -S (Nippon Chemical Industry Co., Ltd.) and the like.

For the purpose of improving the cleaning property, the conductive fine particles should have a primary particle size exceeding 30 nm (preferably having a specific surface area of less than 50 m ² / g), more preferably a primary particle size of 50 nm or more (preferably having a specific surface area of at least 50 nm ² / g). Is less than 30 m ² / g), which is also a preferred embodiment. For example, spherical silica particles, spherical polymethylsilsesquioxane particles, spherical resin particles and the like are preferably used.

The volume average particle size and the particle size distribution of the conductive fine particles in the present invention are measured in a measuring range of 0.04 to 2000 μm by attaching a liquid module to a laser diffraction type particle size distribution measuring device LS-230 manufactured by Coulter Co., Ltd. Can be implemented. As a measuring method, pure water 10 ml
, A 10 mg sample of conductive fine particles is added thereto, and the mixture is dispersed for 10 minutes with an ultrasonic dispersing machine (ultrasonic homogenizer), and then the measurement is performed for 90 seconds and one measurement. Method.

In the present invention, as a method for adjusting the particle size and particle size distribution of the conductive fine particles, the manufacturing method and the manufacturing conditions are set so that the desired particle size and particle size distribution of the primary particles of the conductive fine particles can be obtained at the time of manufacturing. In addition to the method, a method of aggregating small primary particles, a method of pulverizing large primary particles, a method of classification, and the like are possible. Further, the conductive fine particles are applied to part or all of the surface of the base particles having the desired particle size and particle size distribution (particles serving as a base when attaching or fixing the conductive material in preparing the conductive fine particles). How to attach or fix,
It is also possible to use a method using conductive fine particles having a form in which a conductive component is dispersed in particles having a desired particle size and particle size distribution, and it is also possible to adjust the particle size and particle size distribution of the conductive fine particles by combining these methods. It is possible.

When the particles of the conductive fine particles are formed as aggregates, the average particle size of the aggregates is defined as the volume average particle size of the conductive fine particles. There is no problem that the conductive fine particles exist not only in the state of primary particles but also in the state of aggregation of secondary particles. Regardless of the state of aggregation, the form is not particularly limited as long as it can be provided as an aggregate in the contact portion between the charging member and the image carrier or in a charging region in the vicinity thereof and realize the function of assisting or promoting charging.

In the present invention, the resistance of the conductive fine particles can be measured by the tablet method and normalized. That is, about 0.5 in a cylinder having a bottom area of 2.26 cm ^2.
g of the conductive fine particle sample, pressurize the upper and lower electrodes by 15 kg and simultaneously apply a voltage of 100 V to measure the resistance value.
Thereafter, the specific resistance is calculated by normalization.

The magnetic toner used in the present invention may further contain other additives, for example, lubricant powders such as Teflon powder, zinc stearate powder, polyvinylidene fluoride powder, or cerium oxide within a range that does not substantially adversely affect the toner. Abrasives such as powders, silicon carbide powders, strontium titanate powders, or fluidity-imparting agents such as titanium oxide powders and aluminum oxide powders, anti-caking agents, and improving the developability of organic and inorganic fine particles of opposite polarity. A small amount can be used as an agent. These additives can also be used after the surface is hydrophobized by the method described above.

Further, other coloring agents may be used in addition to the magnetic substance. Coloring materials that can be used in combination include magnetic or non-magnetic inorganic compounds, known dyes and pigments. Specifically, for example, cobalt, ferromagnetic metal particles such as nickel, or chromium, manganese, copper, zinc,
Examples include alloys containing aluminum and rare earth elements, particles such as hematite, titanium black, nigrosine dye / pigment, carbon black, and phthalocyanine. These may also be used after treating the surface. <2> Characteristics of Magnetic Toner of the Present Invention The toner of the present invention can be obtained from at least the above-mentioned raw materials.

The average circularity of the magnetic toner of the present invention is 0.970 or more. The reason is as follows.

A toner composed of a toner having an average circularity of 0.970 or more (powder composed of toner particles) is very excellent in transferability. It is considered that this is because the contact area between the toner particles and the photoconductor is small, and the adhesive force of the toner particles to the photoconductor due to the image force, Van der Waals force, and the like is reduced. Therefore, when such toner is used, the transfer residual toner is greatly reduced, so that the toner at the pressure contact portion between the charging member and the photoconductor is extremely small, and the photoconductor is prevented from being scraped and the toner fusion is prevented, and an image defect is prevented. It is thought to be significantly suppressed. Furthermore, since the toner particles in the toner having an average circularity of 0.970 or more have almost no edge portion on the surface, the toner does not scratch the photoconductor surface at the pressure contact portion between the charging member and the photoconductor.
It is also possible to suppress the shaving of the photoconductor surface.

At this time, in the circularity distribution of the toner, the mode circularity is more preferably 0.990 or more. When the mode circularity is 0.990 or more, it means that most of the toner particles have a shape close to a true sphere,
The effect of suppressing the photoreceptor scraping and image defects as described above becomes more remarkable.

These effects become more prominent in an image forming method including a contact transfer step in which omission is likely to occur during transfer.

The average circularity and mode circularity of the magnetic toner can be determined as follows.

In the present invention, the average circularity is used as an index for quantitatively expressing the shape of the particles. In the present invention, the flow particle image analyzer “FPI” manufactured by Toa Medical Electronics Co., Ltd.
A-1000 ", and the circularity (a) of each particle measured for a particle group having a circle equivalent diameter of 3 μm or more.
i) is determined by the following formula (I), and the value obtained by dividing the total circularity of all the particles measured by the following formula (II) by the total number of particles (m) is defined as an average circularity (am). Define.

[0196]

Circularity (ai) = L ₀ / L Formula (I) (where L ₀ represents the circumference of a circle having the same projected area as the magnetic toner particle image, and L is the projected image of the magnetic toner particle) Indicates the perimeter of.)

[0197]

(Equation 2) The mode circularity means that the circularity is from 0.40 to 1.0.
The circularity of each measured particle is divided into 61 by 0 to 0, and the measured circularity of each particle is assigned to each divided range. The circularity of the peak having the maximum frequency value in the circularity frequency distribution.

The measuring apparatus “F” used in the present invention
After calculating the circularity of each particle, the PIA-1000 calculates the average circularity and the mode circularity, and calculates the circularity from 0.40 to 1.00 by 61 according to the obtained circularity.
A calculation method is used in which the average circularity and the mode circularity are calculated using the center value and the frequency of the division points, divided into the divided classes. However, an error between each value of the average circularity and the mode circularity calculated by this calculation method and each value of the average circularity and the mode circularity calculated by the above-described calculation formula directly using the circularity of each particle. Is very small and substantially negligible, and in the present invention, for the reasons of data handling such as shortening of calculation time and simplification of calculation formula, each particle described above is used. Such a calculation method that is partially modified using the concept of a calculation formula that directly uses circularity may be used.

The measurement procedure is as follows.

About 10 mg of a magnetic toner is dispersed in 10 ml of water in which about 0.1 mg of a surfactant is dissolved to prepare a dispersion, and the dispersion is irradiated with ultrasonic waves (20 KHz, 50 W) for 5 minutes. With the liquid concentration being 5,000 to 20,000 / μl, measurement is carried out by the above-mentioned apparatus, and the average circularity and mode circularity of a group of particles having a circle equivalent diameter of 3 μm or more are determined.

The average circularity in the present invention is an index of the degree of unevenness of the magnetic toner. The average circularity is 1.000 when the magnetic toner has a perfect spherical shape. It will be a small value.

The reason why the circularity was measured only for particles having a circle equivalent diameter of 3 μm or more in this measurement is that 3 μm.
This is because the particle group having a circle equivalent diameter of less than m includes a large number of particles of the external additive which are present independently of the toner particles, so that the circularity of the toner particles cannot be accurately estimated due to the influence. .

Further, the ratio (B / B) of the iron element abundance (B) to the carbon element abundance (A) present on the surface of the magnetic toner particles measured by X-ray photoelectron spectroscopy of the magnetic toner of the present invention. A) is less than 0.001.

As described above, in the image forming method including the contact charging step, when the magnetic toner having the magnetic material exposed on the surface of the toner particles is used, the shaving of the photosensitive member by the exposed magnetic material becomes more remarkable. Easy to appear. However, if (B / A) is less than 0.001 as described above, that is, if a magnetic toner in which the magnetic substance is hardly exposed on the surface of the toner particles is used, even if the toner is pressed against the surface of the photoreceptor by the charging member, The surface of the photoconductor is hardly scraped, and the shaving of the photoconductor and toner fusion can be significantly reduced. Of course, the effect is remarkable even in an image forming method combining a contact transfer step, and an extremely high-definition image can be obtained for a long period of time. Furthermore, it is more preferable that (B / A) is less than 0.0005, because high image quality and durability stability are remarkably improved.

The ratio of the content (B) of the iron element (B) to the content (A) of the carbon element present on the surface of the magnetic toner (B
/ A) can be calculated by performing surface composition analysis by ESCA (X-ray photoelectron spectroscopy).

In the present invention, the ESCA apparatus and measurement conditions are as follows. Apparatus used: 1600S type X-ray photoelectron spectrometer manufactured by PHI Measurement conditions: X-ray source MgKα (400 W) Spectral region 800 μmφ In the present invention, PH is determined from the measured peak intensity of each element.
The surface atomic concentration is calculated using the relative sensitivity factor provided by Company I. In this measurement, it is preferable that the toner is subjected to ultrasonic cleaning to remove inorganic fine particles adhering to the surface of the magnetic toner particles, separated by a magnetic force, dried and measured.

The preferred state of dispersion of the magnetic material in the magnetic toner particles is a state in which the magnetic particles are present in the entire toner particles as much as possible without being agglomerated, which is also the magnetic toner according to the image forming method of the present invention. The basis of the features.

In the present invention, when the diameter equivalent to the projected area circle of the magnetic toner is C, and the minimum value of the distance from the surface of the magnetic material in cross-sectional observation of the magnetic toner using a transmission electron microscope (TEM) is D. , D / C ≦ 0.02 or less, the number of toner particles is preferably 50% by number or more, more preferably 65% by number or more, even more preferably 75% by number or more.

The reason is as follows.

When the conditions of the present invention are not satisfied, no magnetic material exists at least outside the boundary of D / C = 0.02 in all the toner particles. Assuming that the above particles are spherical, 1
When one toner particle is the entire space, the space where the magnetic substance does not exist is at least 11.5% on the surface side of the toner particle.
Will exist. Actually, since the magnetic substance is not uniformly arranged at the closest position to form an inner wall inside the toner particle, it is apparent that the magnetic substance is 12% or more.

If the magnetic substance does not exist in such a space per particle, the magnetic substance is biased inside the toner particles, and the possibility of agglomeration of the magnetic substance is extremely increased. As a result, the coloring power is reduced. Although the specific gravity of the toner particles increases according to the content of the magnetic substance, the binder resin and the wax component are unevenly distributed on the surface of the toner particles. Therefore, even if a surface layer is provided on the outermost surface of the toner particles by some means, if stress or the like is applied to the toner particles or the toner particles during the production of the toner, fusion or deformation is likely to occur, and handling in the production is complicated. And the distribution of the powder characteristics of the toner obtained by the deformation is increased, which adversely affects the electrophotographic characteristics and increases the possibility that the blocking property during storage of the toner is deteriorated. In a particle structure in which the toner particles have only the binder resin and wax and the magnetic substance is unevenly distributed inside, the external surface of the toner particles is soft and the inside is hard. The sex worsens. The risk of causing such adverse effects increases.

When the number of toner particles satisfying D / C ≦ 0.02 is 5
If it is less than 0%, the above-mentioned adverse effects such as a decrease in coloring power, a deterioration in blocking property and a deterioration in durability tend to be remarkable. Therefore, in the present invention, D / C ≦ 0.0
It is preferable that the number of toner particles satisfying 2 is 50% or more.

In the present invention, as a method of adjusting D / C ≦ 0.02, the particle diameter contained in the magnetic material may be 0.03 to 0.1.
Examples include reducing the ratio of particles having a particle size in the range of μm or particles having a particle size of 0.3 μm or more, and controlling the type and uniformity of the surface treatment agent for the magnetic material.

In the present invention, the projected area circle equivalent diameter C of the magnetic toner can be measured with a Coulter Multisizer described later, and D can be measured as follows. As a specific observation method using a TEM, after sufficiently dispersing the toner particles to be observed in a room temperature curable epoxy resin,
It is preferable to use a method in which a cured product obtained by curing in an atmosphere at a temperature of 40 ° C. for 2 days as it is or frozen and observed as a flaky sample by a microtome provided with diamond teeth.

A specific method for determining the ratio of the number of the corresponding toner particles is as follows. D / in TEM
For the toner particles for determining C, the equivalent circle diameter is determined from the cross-sectional area in a micrograph, and the value is ± 10% of the number average particle diameter.
And the minimum value (D) of the distance between the surface of the magnetic material and the surface of the magnetic toner particle is measured for the corresponding toner particle, and D / C is calculated.
The ratio of the magnetic toner particles having a D / C value calculated in this way of 0.02 or less is defined to be determined by the following equation (III). The micrograph at this time is preferably at a magnification of 10,000 to 20,000 times in order to perform highly accurate measurement. In the present invention, a transmission electron microscope (H-600 manufactured by Hitachi) is used as an apparatus, and observation is performed at an acceleration voltage of 100 kV.
Observe / measure using a microphotograph of 10,000 times.

[0216]

(Equation 3) The magnetic toner of the present invention has a magnetic field of 79.6 kA / m.
(1000 Oersted) with a magnetization intensity of 10
It is a magnetic toner of 50 Am ² / kg (emu / g). The magnetic toner can prevent the leakage of the toner by providing the magnetic force generating means in the developing device, and can enhance the toner transporting property or the stirring property. Further, by providing a magnetic force generating means so that a magnetic force acts on the toner carrier, the recoverability of the transfer residual toner is further improved, and the magnetic toner forms spikes to prevent the toner from scattering. Becomes easier.

However, if the intensity of magnetization of the toner in a magnetic field of 79.6 kA / m is less than 10 Am ² / kg, the above-mentioned effect cannot be obtained. Fog, uneven image density due to non-uniform charge application to the toner,
Image defects such as defective collection of transfer residual toner are likely to occur. If the magnetic strength of the magnetic toner at a magnetic field of 79.6 kA / m is larger than 50 Am ² / kg, when a magnetic force is applied to the toner, the fluidity of the toner is significantly reduced due to magnetic aggregation, and the transferability is reduced. The increase in the amount of untransferred toner and the tendency of the toner particles and the conductive fine particles to behave together reduce the amount of conductive fine particles attached to and mixed into the contact charging member and reduce the amount of conductive fine particles present in the charging section. The amount is also relatively reduced with respect to the transfer residual toner amount, so that fogging and image contamination due to a decrease in chargeability tend to occur. Further, the magnetic toner of the present invention further has an average circularity of 0.970 or more, so that the toner ears on the toner carrier become thinner and denser, the charging becomes uniform, and the fog is greatly reduced. I do.

In the magnetic toner of the present invention, the range of the particle diameter is not particularly limited.
To faithfully develop finer latent image dots, the weight average particle diameter of the magnetic toner is preferably 3 to 10 μm.

In the case of a magnetic toner having a weight average particle diameter of less than 3 μm, the transfer residual toner on the photoreceptor is increased due to a decrease in transfer efficiency, and the abrasion of the photoreceptor and suppression of toner fusion in the contact charging step are suppressed. It becomes difficult. Furthermore, in addition to an increase in the surface area of the entire magnetic toner, the fluidity and agitation of the powder are reduced, and the tendency of the toner particles and the conductive fine particles to behave together is increased. Therefore, the amount of conductive fine particles adhering to and mixing with the contact charging member and intervening in the charging portion is reduced. For this reason, the chargeability inhibition due to the transfer residual toner becomes relatively large, and it is impossible to maintain the chargeability, and the chargeability cannot be maintained, resulting in fog and image contamination. Since it is difficult to uniformly charge the individual toner particles as described above, fogging and transferability tend to be deteriorated, and it is likely to cause non-uniform unevenness of an image other than abrasion and fusion, so that the toner is used in the present invention. It is not preferable for the magnetic toner to be used. If the weight average particle diameter of the magnetic toner exceeds 10 μm, characters and line images are liable to be scattered, and it is difficult to obtain high resolution. In addition, the charge amount of the toner particles is liable to be greatly reduced due to the increase in the content of the conductive fine particles, and the amount of the conductive fine particles interposed in the charging portion is reduced by the close contact property and the contact resistance of the contact charging member to the image carrier. When the content of the conductive fine particles in the toner is set to such an extent that the toner can be maintained, the chargeability of the toner particles is reduced, thereby deteriorating the developability of the entire toner. Even a slight segregation of the conductive fine particles in the developing unit due to the collection of a large amount of toner may cause a significant decrease in image density due to a significant decrease in image density.
In order to maintain more stable chargeability and developability, it is preferable that the weight average particle diameter of the toner is 4.0 to 8.0 μm or less.

Here, the weight average particle size of the magnetic toner can be measured by various methods such as Coulter Counter TA-II or Coulter Multisizer (manufactured by Coulter). In the present invention, the Coulter Multisizer (Coulter Multisizer) is used. Interface (manufactured by Nikkaki) and PC9801 that output the number distribution and volume distribution using
A personal computer (manufactured by NEC) is connected, and a 1% aqueous solution of NaCl is adjusted using primary grade sodium chloride as an electrolytic solution. For example, ISOTON R-II (manufactured by Coulter Scientific Japan) can be used.

The measuring method is as follows.
0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersing agent to 150 ml, and 2 to 20 mg of a measurement sample is further added. The electrolytic solution in which the sample was suspended was subjected to dispersion treatment for about 1 to 3 minutes using an ultrasonic disperser, and the volume and number of toner particles having a size of 2 μm or more were measured using the Coulter Multisizer with a 100 μm aperture as the aperture. And the number distribution are calculated.

Then, the volume-based weight average particle diameter (D4) and volume average particle diameter (DV) determined from the volume distribution and the number-based length average particle diameter determined from the number distribution in the present invention, that is, the number average particle The diameter (D1) can be determined.

Incidentally, the resistance of the magnetic toner particles of the present invention is as follows.
Preferably, it is 1 × 10 ¹⁰ Ω · cm or more.
More preferably, it is at least 0 ¹² Ω · cm. If the toner particles do not substantially exhibit insulation, it is difficult to achieve both developability and transferability. Further, charge is easily injected into the toner particles due to the development electric field, and the charge of the toner is disturbed to cause fog. <3> Manufacturing method of magnetic toner of the present invention When manufacturing the magnetic toner of the present invention by a pulverization method, a known method is used.
Heating roll, kneader, extruder after sufficiently mixing a magnetic substance, a release agent, a charge control agent, a component necessary as a toner such as a colorant, and other additives with a mixer such as a Henschel mixer or a ball mill. Melt and knead using a hot kneading machine as described above, and further disperse or dissolve other magnetic toner materials such as magnetic substances as necessary while the binder resins are mutually compatible, and then cool and solidify and pulverize. Thereafter, classification and, if necessary, surface treatment are performed to obtain magnetic toner particles, and the magnetic toner of the present invention can be obtained by adding and mixing inorganic fine particles and the like. Either the classification or the surface treatment may be performed first. In the classification step, it is preferable to use a multi-division classifier in terms of production efficiency.

The pulverizing step can be performed by a method using a known pulverizing apparatus such as a mechanical impact type and a jet type.
In the present invention, in order to obtain a magnetic toner having a specific degree of circularity, it is preferable to further apply heat to pulverize or supplementarily apply a mechanical impact.
Further, a hot water bath method in which finely pulverized (classified as necessary) magnetic toner particles are dispersed in hot water, a method in which the toner particles pass through a hot air stream, or the like may be used.

As a means for applying a mechanical impact force, for example, a method using a mechanical impact pulverizer such as a Kryptron system manufactured by Kawasaki Heavy Industries and a turbo mill manufactured by Turbo Kogyo, a mechano-fusion system manufactured by Hosokawa Micron Corp. Like a device such as a hybridization system manufactured by Nara Machinery Co., Ltd., the toner is pressed against the inside of the casing by centrifugal force by a high-speed rotating blade, and a mechanical impact force is applied to the toner by a force such as a compressive force or a frictional force. No.

In the case where the mechanical impact method is used, the processing temperature is set to a temperature around the glass transition point Tg of the magnetic toner (T
g ± 30 ° C.) is preferable from the viewpoint of preventing aggregation and productivity. More preferably, the transfer is performed at a temperature in the range of the glass transition point Tg ± 20 ° C. of the magnetic toner, which is particularly effective for improving the transfer efficiency.

Furthermore, the magnetic toner of the present invention can be prepared by a method described in Japanese Patent Publication No. 56-13945, which uses a disk or a multi-fluid nozzle to atomize a molten mixture into air to obtain a spherical toner. The polymer is typically represented by a dispersion polymerization method in which an aqueous organic solvent in which the obtained polymer is insoluble is used to directly produce a toner, or a soap-free polymerization method in which a toner is produced by directly polymerizing in the presence of a water-soluble polar polymerization initiator. It can also be produced by a method of producing a toner using an emulsion polymerization method or the like.

The magnetic toner according to the present invention can be produced by the above-mentioned pulverization method. However, the toner particles obtained by this pulverization method are generally irregular in shape, and the essential properties of the magnetic toner according to the present invention are essential. In order to obtain the physical property that the average circularity is 0.970 or more, which is a requirement, and more preferable physical property that the mode circularity is 0.990 or more, it is necessary to perform mechanical / thermal or some special processing. . Furthermore, the pulverization method essentially exposes magnetic iron oxide particles to the surface of the toner particles, which is an essential condition for the magnetic toner of the present invention. The carbon element present on the surface measured by X-ray photoelectron spectroscopy is essential. The ratio (B / A) of the iron element content (B) to the iron content (A) is 0.0
It is difficult to obtain a magnetic toner of less than 01, and the problem of scraping of the photoconductor may not be solved in some cases.

Therefore, in order to solve the above-mentioned problems, in the present invention, after the toner particles are produced by a polymerization method, particularly a suspension polymerization method, the inorganic particles are adhered to the surface by mixing and adding the inorganic particles. Preferably, the magnetic toner of the present invention is used. In this suspension polymerization method, a polymerizable monomer and a colorant (and, if necessary, a polymerization initiator, a crosslinking agent, a charge control agent, and other additives) are uniformly dissolved or dispersed to prepare a monomer composition. After that, this monomer composition is dispersed in a continuous layer containing a dispersion stabilizer (for example, an aqueous phase) using a suitable stirrer, and simultaneously undergoes a polymerization reaction to obtain a toner having a desired particle size. What you get. Magnetic toner particles obtained by this suspension polymerization method (hereinafter referred to as “polymerized toner”)
Is also referred to as), since the individual toner particle shapes are substantially spherical, it is easy to obtain a magnetic toner having an average circularity of 0.970 or more and satisfying the physical property requirements essential to the present invention.
Furthermore, such a magnetic toner has a high transferability because the distribution of the charge amount is relatively uniform.

However, even when a normal magnetic substance is contained in the polymerized toner, it is difficult to suppress the exposure of the magnetic substance from the particle surface. Further, not only the fluidity and charging characteristics of the toner particles are significantly reduced, but also the toner having an average circularity of 0.970 or more is obtained due to the strong interaction between the magnetic substance and water during the production of the suspension polymerization toner. It is hard to be. This is firstly that the magnetic particles are generally hydrophilic and therefore easily present on the toner surface. Secondly, the magnetic particles move randomly when the aqueous solvent is stirred, and the suspended particles composed of monomers It is considered that the surface is dragged, the shape is distorted, and it is difficult to form a circle. In order to solve these problems, it is important to modify the surface characteristics of the magnetic particles. Since the magnetic substance has excellent hydrophobicity and dispersibility, the magnetic substance used in the polymerized toner in the present invention is the above-mentioned magnetic substance whose surface is treated while hydrolyzing the coupling agent in an aqueous medium. Is preferred. When the magnetic material is used as a material for a polymerized toner, the dispersibility in the toner particles becomes very good, and a magnetic toner having a substantially spherical shape can be obtained without exposing the magnetic material to the surface of the toner particles. . That is, the average circularity is 0.970 or more, and the mode circularity is 0.990 or more, and the content (A) of the carbon element present on the surface of the magnetic toner (A) measured by X-ray photoelectron spectroscopy is (B). It is possible to obtain a magnetic toner having a ratio (B / A) of less than 0.001.

A method for producing the magnetic toner of the present invention by a suspension polymerization method will be described.

The polymerizable monomers constituting the polymerizable monomer system used in the polymerized toner according to the present invention include those described above.

In the production of the polymerized toner according to the present invention, a resin may be added to the polymerizable monomer containing the polymerizable monomer for polymerization. For example, the monomer contains a hydrophilic functional group such as an amino group, a carboxylic acid group, a hydroxyl group, a sulfonic acid group, a glycidyl group, and a nitrile group, which cannot be used because it dissolves in an aqueous suspension to cause emulsion polymerization due to water solubility. When it is desired to introduce the monomer component into the toner, a random copolymer, a block copolymer, or a graft copolymer of these and a vinyl compound such as styrene or ethylene, in the form of a copolymer, or a polyester , Polycondensates such as polyamides and polyaddition polymers such as polyethers and polyimines. When such a high molecular polymer containing a polar functional group is coexisted in the toner, the above-mentioned wax component is phase-separated, and the encapsulation becomes stronger,
A toner having good offset resistance, blocking resistance and low-temperature fixability can be obtained. When a high molecular polymer containing such a polar functional group is used, the number average molecular weight is preferably 5,000 or more. When the molecular weight is 5,000 or less, particularly 4,000 or less, the present polymer tends to concentrate near the surface, so that adverse effects on developability, blocking resistance, and the like are likely to occur, which is not preferable.

Further, a resin other than the above may be added to the polymerizable monomer system for the purpose of improving the dispersibility and fixing property of the material, or the image characteristics, and the like.
For example, polystyrene, a homopolymer of styrene such as polyvinyltoluene and a substituted product thereof; a styrene-propylene copolymer, a styrene-vinyltoluene copolymer, a styrene-vinylnaphthalene copolymer, a styrene-methyl acrylate copolymer, Styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-
Octyl acrylate copolymer, styrene-dimethylaminoethyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene- Dimethylaminoethyl methacrylate copolymer,
Styrene-vinyl methyl ether copolymer, styrene-
Styrenes such as vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer Copolymer: polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyethylene, polypropylene, polyvinyl butyral, silicone resin, polyester resin, polyamide resin, epoxy resin, polyacrylic resin, rosin, modified rosin, terpene resin, phenol resin , Aliphatic or alicyclic hydrocarbon resins, aromatic petroleum resins and the like can be used alone or in combination.

The addition amount of these resins is as follows.
1 to 20 parts by mass relative to 0 parts by mass is preferred. If the amount is less than 1 part by mass, the effect of addition is small, while if it is more than 20 parts by mass, it tends to be difficult to design various physical properties of the polymerized toner.

Further, if a polymer having a molecular weight different from the molecular weight range of the magnetic toner obtained by polymerizing the monomer is dissolved in the monomer and polymerized, a toner having a wide molecular weight distribution and high offset resistance can be obtained. Can be obtained.

As the polymerization initiator used when the magnetic toner of the present invention is produced by a polymerization method, a polymerization initiator having a half life of 0.5 to 30 hours at the time of the polymerization reaction is added to 100 parts by mass of the polymerizable monomer. On the other hand, when the polymerization reaction is carried out with an addition amount of 0.5 to 20 parts by mass, a polymer having a maximum molecular weight of 10,000 to 100,000 can be obtained, and the desired strength and appropriate melting characteristics can be imparted to the toner.

Specific examples of such a polymerization initiator include:
2,2′-azobis- (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile,
Diazo polymerization such as azo polymerization initiator such as 1'-azobis (cyclohexane-1-carbonitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile and azobisisobutyronitrile Initiator or peroxide such as benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide, t-butylperoxy 2-ethylhexanoate System polymerization initiator.

When the magnetic toner of the present invention is produced by a polymerization method, a crosslinking agent may be added. A preferable addition amount is 0.001 to 100 parts by mass of the polymerizable monomer.
１５15 parts by mass.

As the cross-linking agent, compounds having two or more polymerizable double bonds are mainly used, for example, aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene, etc .; Ethylene glycol dimethacrylate,
Carboxylic acid esters having two double bonds such as 1,3-butanediol dimethacrylate; divinyl compounds such as divinylaniline, divinyl ether, divinyl sulfide and divinyl sulfone; and compounds having three or more vinyl groups; Are used alone or as a mixture.

When the magnetic toner of the present invention is produced by a polymerization method, the magnetic toner, the release agent, the plasticizer, the charge control agent and the crosslinking agent are generally added to the above-mentioned toner composition, that is, the polymerizable monomer. Components necessary as a toner such as a colorant and other additives, for example, an organic solvent to be added to reduce the viscosity of the polymer formed in the polymerization reaction, a high-molecular polymer, a dispersant and the like, as appropriate, a homogenizer, A polymerizable monomer system uniformly dissolved or dispersed by a disperser such as a ball mill, a colloid mill, a dissolver, and an ultrasonic disperser is suspended in an aqueous medium containing a dispersion stabilizer.
At this time, the particle size of the obtained toner particles becomes sharper by using a high-speed disperser such as a high-speed stirrer or an ultrasonic disperser to quickly obtain the desired toner particle size.

When a magnetic toner is produced by a polymerization method, it is preferable to use a polymerization initiator, but the timing of adding the polymerization initiator is such that the polymerization initiator is added at the same time as other additives are added to the polymerizable monomer. Alternatively, they may be mixed immediately before suspension in an aqueous medium. Immediately after granulation and before initiating the polymerization reaction, a polymerization initiator dissolved in a polymerizable monomer or a solvent can be added. After granulation, stirring may be performed using a normal stirrer to such an extent that the particle state is maintained and the floating and settling of the particles are prevented.

As the dispersion stabilizer used when the magnetic toner of the present invention is produced by a polymerization method, known surfactants and organic / inorganic dispersants can be used. Among them, inorganic dispersants are used to remove harmful ultrafine powder. It is preferably used because it hardly occurs and the dispersion stability is obtained due to its steric hindrance, so that even if the reaction temperature is changed, the stability is hardly lost, the washing is easy, and the toner is hardly adversely affected. Examples of such inorganic dispersants include calcium phosphate, magnesium phosphate, aluminum phosphate, polyvalent metal phosphates such as zinc phosphate, calcium carbonate, carbonates such as magnesium carbonate, calcium metasilicate, calcium sulfate, barium sulfate and the like. Examples include inorganic salts, inorganic oxides such as calcium hydroxide, magnesium hydroxide, aluminum hydroxide, silica, bentonite, and alumina.

[0244] These inorganic dispersants can be used as polymerizable monomers 10
With respect to 0 parts by mass, 0.2 to 20 parts by mass may be used alone. When producing toner particles having a weight average particle size of 5 μm or less, an interface of 0.001 to 0.1 parts by mass is required. An activator may be used in combination.

Examples of the surfactant include sodium dodecylbenzene sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate,
Examples include sodium oleate, sodium laurate, sodium stearate, potassium stearate and the like.

When these inorganic dispersants are used, they may be used as they are, but in order to obtain finer particles, the inorganic dispersant particles can be formed in an aqueous medium. For example, in the case of calcium phosphate, a water-insoluble calcium phosphate can be produced by mixing an aqueous solution of sodium phosphate and an aqueous solution of calcium chloride under high-speed stirring, and more uniform and fine dispersion can be achieved. At this time, a water-soluble sodium chloride salt is simultaneously produced as a by-product, but if the water-soluble salt is present in the aqueous medium, the dissolution of the polymerizable monomer in water is suppressed, and the ultrafine toner due to emulsion polymerization is formed. This is more convenient because it hardly occurs. Since it becomes an obstacle when removing the residual polymerizable monomer at the end of the polymerization reaction, it is better to replace the aqueous medium or to desalinate with an ion exchange resin. The inorganic dispersant can be almost completely removed by dissolving with an acid or alkali after completion of the polymerization.

In the above polymerization step, the polymerization temperature is 40
The polymerization is carried out at a temperature of at least 50 ° C., generally from 50 to 90 ° C. It is preferable to carry out the polymerization in this temperature range, since the release agent and wax to be sealed inside are precipitated by phase separation, and the encapsulation becomes more complete. To consume the remaining polymerizable monomer, if the end of the polymerization reaction,
It is possible to raise the reaction temperature to 90-150 ° C.

After polymerization is completed, the polymerized toner particles are filtered, washed and dried by a known method, mixed with inorganic fine particles and adhered to the surface to obtain a toner.
In addition, it is also a desirable embodiment of the present invention to insert a classifying step into the manufacturing process and cut coarse or fine powder. <4> Image Forming Method of the Present Invention The image forming method of the present invention applies a voltage to a charging member to charge an image carrier, and forms an electrostatic latent image on the charged image carrier. An electrostatic latent image forming step; a developing step of adhering toner on the toner carrier to the electrostatic latent image formed on the image carrier to form a toner image on the image carrier; A transfer step of electrostatically transferring the formed toner image to a transfer material, wherein the image is repeatedly formed on the image carrier. In the magnetic toner according to the present invention, the charging step is a step of charging the image carrier by applying a voltage to a charging member that forms a contact portion with the image carrier and comes into contact with the image carrier. .

According to the present invention, the charging means contacts the charging member so as to form a contact portion with the photosensitive member as the image bearing member.
This is a direct charging method in which a photoconductor is charged by applying a voltage.

Further, by using the toner of the present invention in which the particle diameter and the average circularity of the magnetic material are defined, the magnetic material in the toner is uniformly distributed, the magnetism of the toner is uniform, and the shape of the toner is constant. Since it falls within the distribution, the image forming method of the present invention exhibits good developability and high image quality.

Next, embodiments of the image forming method of the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto.

In FIG. 1, a photosensitive member 1 as an image bearing member
, A primary charging roller 11 serving as a contact charging member
7, developing device 140, transfer roller 114, cleaner 11
6, a register roller 124 and the like are provided. Then, the photoconductor 100 is moved to −70 by the primary charging roller 117.
It is charged to 0V. (Applied voltage is AC voltage -2.0 kV
pp (Vpp: peak-to-peak potential), DC voltage -700 Vd
c) Then, the photoconductor 100 is exposed by irradiating the photoconductor 100 with the laser beam 123 by the laser beam scanner 121. The electrostatic latent image on the photoconductor 100 is developed with a one-component magnetic toner by a developing device 140, and is transferred onto a transfer material by a transfer roller 114 that is in contact with the photoconductor via the transfer material. The transfer material P having the toner image thereon is conveyed to a fixing device 126 by a conveyor belt 125 or the like, and is fixed on the transfer material P.
Further, the toner left partially on the photoconductor is cleaned by the cleaning unit 116. The developing device 140
As shown in FIG. 2, a cylindrical toner carrier 102 (hereinafter, also referred to as a “developing sleeve”) made of a non-magnetic metal such as aluminum or stainless steel is provided near the photoconductor 100. The gap between the photoconductor and the developing sleeve 102 is maintained at about 300 μm by a sleeve / photoconductor gap maintaining member (not shown). This gap can be changed if necessary. In the developing sleeve 102, a magnet roller 104 is fixed and disposed concentrically with the developing sleeve 102. However, the developing sleeve 10
2 is rotatable. The magnet roller 104 is provided with a plurality of magnetic poles as shown in FIG.
Indicates the regulation of the toner coat amount, S2 affects the taking-in / transport of the toner, and N2 affects the prevention of the blowing of the toner. An elastic blade 103 is provided as a member that regulates the amount of magnetic toner adhered and conveyed to the developing sleeve 102, and the amount of toner conveyed to the developing area is controlled by the contact pressure of the elastic blade 103 against the developing sleeve 102. You. In the developing area, a DC bias voltage and an AC voltage developing bias are applied between the photoconductor 100 and the developing sleeve 102, and the toner on the developing sleeve 102 is changed according to the electrostatic latent image.
It flies above 00 and becomes a visible image.

As a preferable process condition when the charging roller is used as shown in FIG. 1, the contact pressure of the roller is set to 4.
A DC voltage of 9 to 490 N / m (5 to 500 g / cm) or a DC voltage with an AC voltage superimposed thereon is used. When a voltage obtained by superimposing an AC voltage on a DC voltage is used, an AC voltage = 0.5 to 5 kVpp and an AC frequency = 50
５5 kHz, DC voltage = ± 0.2〜 ± 5 kV are preferred.

In the charging step in the image forming method of the present invention, in addition to the roller type (charging roller) as the primary charging roller shown in FIG. A contact portion is formed and brought into contact with a conductive charging member (contact charging member / contact charger) such as a magnetic brush type or a blade type (charging blade), and a predetermined charging bias is applied to the contact charging member. And a contact charging device for charging the photoreceptor surface to a predetermined polarity and potential. These contact charging members also have the effect of eliminating the need for high voltage and reducing the generation of ozone.

Although good charging properties can be obtained by applying only a DC voltage to the contact charging member, an AC voltage (alternating voltage) is superimposed on a DC voltage as in the above-described apparatus shown in FIG. Is also good.

The AC voltage at this time is 2 × Vth (Vt
h: It is preferable to have a peak voltage less than (discharge start voltage when DC voltage is applied) (V).

If the peak voltage of the AC voltage applied to the DC voltage is not less than 2 × Vth, the potential on the image carrier may become unstable, which is not preferable. As an AC voltage when applying a bias in which an AC voltage is superimposed on a DC voltage, the AC voltage more preferably has a peak voltage less than Vth. Thereby, the image carrier can be charged without a substantial discharge phenomenon.

As the waveform of the AC voltage, a sine wave, a rectangular wave, a triangular wave, or the like can be used as appropriate. Alternatively, a pulse wave formed by periodically turning on / off a DC power supply may be used. As described above, as the waveform of the AC voltage, a bias whose voltage value periodically changes can be used.

In the present invention, it is preferable that the charging member has elasticity in providing a contact portion for interposing conductive fine particles between the charging member and the image carrier, and a voltage is applied to the charging member. It is preferable that the conductive member is electrically conductive in order to charge the image carrier. Therefore, the charging member is a conductive elastic roller, a magnetic brush contact member having a magnetic brush portion in which magnetic particles are magnetically constrained, and a magnetic brush contact charging member in which the magnetic brush portion is brought into contact with a photoreceptor or a brush made of conductive fibers. It is preferable and preferable.

In the image forming method of the present invention, the developing step includes an image forming simultaneous cleaning step or a cleaner-less step which also serves as a cleaning step for collecting the toner remaining on the photoreceptor after transferring the toner image onto the transfer material. The method is also preferable.

Further, in the simultaneous cleaning image forming method or the cleanerless image forming method, the developing step is a step of developing an electrostatic latent image on the image carrier with toner, and the charging step is a step of contacting the image carrier with a contact portion. Is a step of charging the image carrier by applying a voltage to the charging member that comes into contact with the toner, and the magnetic toner of the present invention is provided at least at the contact portion between the charging member and the image carrier and / or in the vicinity thereof. It is preferable that the image forming method is such that the conductive fine particles contained therein adhere to the image carrier in the developing step, remain on the image carrier after the transfer step, and are carried and interposed.

First, the behavior of the toner particles and the conductive fine particles during the image forming process when the conductive fine particles are externally added to the magnetic toner particles in the developing simultaneous cleaning image forming method will be described.

In the developing step, an appropriate amount of the conductive fine particles included in the toner is transferred to the electrostatic latent image on the image carrier together with the toner particles to the image carrier side.

The toner image on the image carrier is transferred to the transfer material in the transfer step. A part of the conductive fine particles on the image carrier also adhere to the transfer material side, but the rest remains adhered and held on the image carrier. When a transfer is performed by applying a transfer bias having a polarity opposite to that of the toner, the toner is attracted to the transfer material and is positively transferred, but since the conductive fine particles on the image carrier are conductive, It does not actively transfer to the transfer material side,
Although a part adheres to the transfer material side, the rest remains adhered and held on the image carrier.

In the image forming method without using a cleaner, the transfer residual toner remaining on the surface of the image carrier after the transfer and the above-mentioned residual conductive fine particles are transferred to the charging section which is the contact portion between the image carrier and the contact charging member. It is carried as it is by the movement of the carrier surface, and adheres to and mixes with the contact charging member. Therefore, contact charging of the image carrier is performed in a state where the conductive fine particles are interposed in the contact portion between the image carrier and the contact charging member.

The presence of the conductive fine particles enables the contact charging member to maintain close contact and contact resistance with the image carrier irrespective of contamination due to adhesion and mixing of transfer residual toner to the contact charging member. The image carrier can be favorably charged by the contact charging member. Further, the transfer residual toner adhering to and mixed into the contact charging member is uniformly charged to the same polarity as the charging bias by the charging bias applied from the charging member to the image carrier, and is gradually transferred from the contact charging member onto the image carrier. Is discharged to the developing unit with the movement of the surface of the image carrier, and is cleaned (collected) at the same time as the development in the developing process.

Further, as the image formation is repeated, the conductive fine particles contained in the toner move to the image carrier surface in the developing section, and are carried to the charging section via the transfer section by the movement of the image carrying surface. Since the conductive fine particles continue to be supplied to the charging unit sequentially, even if the conductive fine particles are dropped or deteriorated due to dropping or the like in the charging unit, it is possible to prevent the deterioration of the charging property and prevent the fine particles from being charged. Sex is maintained stably.

As a further problem to be solved, in the conventional image forming method, conductive fine particles are positively present in the contact portion between the image carrier and the contact charging member, and the insulating transfer to the contact charging member is performed. When the toner contains a necessary amount of conductive fine particles to overcome the charge inhibition due to adhesion and mixing of the residual toner and to perform good charging of the image carrier, the toner is used until the toner amount in the toner cartridge becomes small. In this case, good image quality may not be maintained due to a decrease in image density or an increase in fog.

Even in a conventional image forming apparatus having a cleaning mechanism, when conductive fine particles are contained in toner, the conductive fine particles are selectively consumed in the developing step, or conversely, the conductive fine particles remain. Due to the segregation of the conductive fine particles in the toner due to this, when the toner cartridge is used until the toner amount is reduced in the toner cartridge, the image density may decrease or the fog may increase. For this reason, it is known that, by fixing conductive fine particles to toner particles, selective consumption or segregation of the conductive fine particles is reduced, and a decrease in image density and a decrease in image quality due to an increase in fog are known. ing.

On the other hand, when a toner containing conductive fine particles is applied to a simultaneous cleaning image forming method for development, segregation of the conductive fine particles has a greater effect on image characteristics. That is, as described above, the conductive fine particles contained in the toner are transferred to the image carrier side in an appropriate amount together with the toner particles in the developing process, and then the conductive fine particles on the image carrier are partially transferred in the transfer process. Although the toner adheres to the material side, the remainder is adhered and held on the image carrier and remains. When transfer is performed by applying a transfer bias, the toner particles are attracted to the transfer material side and positively transfer, but the conductive fine particles on the image carrier are conductive and thus are transferred to the transfer material side. Does not positively transfer, and a part adheres to the transfer material side, but the rest remains adhered and held on the image carrier. In the image forming method without using a cleaner, the transfer residual toner remaining on the surface of the image carrier after the transfer and the above-mentioned residual conductive fine particles adhere to and mix in the contact charging member. At this time, the ratio of the amount of the conductive fine particles adhering to and mixed into the contact charging member with respect to the transfer residual toner is determined by the difference in the transferability between the conductive fine particles and the toner particles. Will obviously increase. In this state, the conductive fine particles adhering to and mixed into the contact charging member are gradually discharged from the contact charging member together with the transfer residual toner onto the image carrier, move to the image carrier surface, and reach the developing section. It is cleaned (collected). That is, the toner having a significantly high ratio of the conductive fine particles is recovered by the simultaneous cleaning with development, so that the segregation of the conductive fine particles is greatly accelerated, and the image quality is significantly reduced due to a significant decrease in image density.

On the other hand, as in the case of the image forming apparatus having the conventional cleaning mechanism, if the conductive fine particles are fixed to the toner particles to reduce the segregation of the conductive fine particles, the conductive fine particles are also required in the transfer step. Since the fine particles behave together with the toner particles, the fine particles are transferred to the transfer material side together with the toner particles. The intervening amount of the conductive fine particles becomes insufficient with respect to the amount of the residual toner, and the chargeability cannot be maintained by overcoming the chargeability inhibition due to the transfer residual toner. Contact property and contact resistance cannot be maintained, and the chargeability of the image carrier by the contact charging member is reduced, which may cause fog and image contamination.

The application of a toner containing conductive fine particles to the simultaneous cleaning image forming method using a contact charging member involves the above-described difficulties. By using a contact charging member capable of reducing the generation of ozone by using a toner having a weight average particle diameter of 3 to 10 μm, a cleaner-less image forming method that does not generate waste toner, the conductive fine particles can be maintained while maintaining good chargeability. Can be greatly reduced, and a decrease in image quality such as a decrease in image density can be improved to a level at which there is no practical problem.

If the amount of the conductive fine particles in the contact portion between the image bearing member and the contact charging member is too small, the lubricating effect by the conductive fine particles cannot be sufficiently obtained, and the contact between the image bearing member and the contact charging member cannot be obtained. And it is difficult to rotationally drive the contact charging member to the image carrier with a speed difference. That is, the driving torque becomes excessively large, and if it is forcibly rotated, the surfaces of the contact charging member and the image carrier will be scraped. Further, the effect of increasing the chance of contact by the conductive fine particles may not be obtained, so that sufficient charging performance cannot be obtained. On the other hand, if the amount is too large, the detachment of the conductive fine particles from the contact charging member is significantly increased, which may adversely affect image formation.

From the above, the amount of the conductive fine particles in the contact portion between the image carrier and the contact charging member is 1 × 10 ³
５5 × 10 ⁵ / mm ² , more preferably 1 ×
10 ⁴ -5 × 10 ⁵ pieces / mm ² is good. 1 × 10 ³ pieces / mm
^If it is lower than ² , a sufficient lubricating effect and an effect of increasing the chance of contact cannot be obtained, and the charging performance may decrease. 1 × 10 ⁴
If the number is smaller than the number of toner particles / mm ² , the charging performance may decrease when the amount of the transfer residual toner is large.

The application density range of the conductive fine particles is also determined by what density the conductive fine particles are applied on the image carrier to obtain the uniform charging effect.

Needless to say, at the time of charging, uniform contact charging is required at least than this recording resolution (resolution of an electrostatic latent image).

However, regarding the visual characteristics of the human eye, when the spatial frequency is 10 cycles / mm or more, the number of discrimination gradations on the image approaches 1 without limit, that is, it becomes impossible to discriminate density unevenness. If this property is positively utilized, conductive fine particles may be present at a density of at least 10 cycles / mm on at least the image carrier when conductive fine particles are adhered on the image carrier, and direct injection charging may be performed. Will be. Even if micro charge failure occurs where no conductive fine particles are present, density unevenness on an image caused by the charge failure occurs in a spatial frequency region exceeding human visual characteristics. There will be no problems.

When the coating density of the conductive fine particles changes, whether or not the charging failure as density unevenness is recognized on the image is determined by applying a small amount of the conductive fine particles (for example, 10 particles / mm). ² ) Although the effect of suppressing the occurrence of charging unevenness is recognized, it is still insufficient in terms of whether density unevenness on an image is acceptable to humans.

However, the coating amount was 1 × 10 ² / mm ²
Then, a favorable result can be rapidly obtained in the objective evaluation of the image. Furthermore, the application amount is 1 × 10 ³
By increasing the number of pieces / mm ² or more, there is no problem on the image due to poor charging.

The charging by the direct injection charging method is fundamentally different from the discharging charging method, and the charging is performed by surely bringing the charging member into contact with the photosensitive member. Even if it is applied excessively on the carrier, there are always parts that cannot be contacted. However, this problem is practically solved by applying the conductive fine particles of the present invention that actively utilize the human visual characteristics.

However, when the direct injection charging method is applied as uniform charging of the image carrier in the simultaneous development and cleaning image formation, the charging characteristics are deteriorated due to the adhesion or mixing of the transfer residual toner to the charging member. In order to suppress the adhesion and mixing of the transfer residual toner to the charging member, or to overcome the adverse effect on the charging characteristics due to the adhesion or mixing of the transfer residual toner to the charging member and perform good direct injection charging, an image carrier It is preferable that the amount of the conductive fine particles present in the contact portion between the contact member and the contact charging member is 1 × 10 ⁴ particles / mm ² or more.

The upper limit of the amount of the conductive fine particles applied is as follows:
This is until the conductive fine particles are uniformly coated on the image carrier in one layer. Even if the conductive fine particles are further applied, the effect is not improved, and conversely, there is a problem that the exposure source is blocked or scattered.

Since the upper limit of the coating density varies depending on the particle size of the conductive fine particles, it cannot be said unconditionally. However, if it is forcibly described, one layer of the conductive fine particles is uniformly coated on the image carrier. Is the upper limit.

The amount of the conductive fine particles was 5 × 10 ⁵ particles / mm ²
When the particle diameter exceeds the above range, the detachment of the conductive fine particles into the image carrier is remarkably increased, and the amount of exposure to the image carrier is insufficient regardless of the light transmittance of the particles themselves. When the number is 5 × 10 ⁵ particles / mm ² or less, the amount of particles falling off can be suppressed low, and the inhibition of exposure can be improved. When the abundance of the particles dropped on the image carrier was measured in the intervening amount range, it was 1 × 10 ² to 1 × 10 ⁵ particles / mm ^2. × 10 ⁴ -5
An intercalation amount of × 10 ⁵ pieces / mm ² is preferable.

A method for measuring the amount of conductive fine particles present in the charging contact portion and the amount of conductive fine particles present on the image carrier in the electrostatic latent image forming step will be described. It is desirable that the amount of the conductive fine particles be measured directly at the contact surface between the contact charging member and the image carrier, but a speed difference is provided between the surface of the contact charging member forming the contact portion and the surface of the image carrier. In this case, since most of the particles present on the image carrier before coming into contact with the contact charging member are peeled off by the charging member coming into contact while moving in the opposite direction, in the present invention, immediately before reaching the contact surface portion The amount of particles on the surface of the contact charging member is defined as the intervening amount.

Specifically, the rotation of the image carrier and the conductive elastic roller is stopped without applying a charging bias, and the surfaces of the image carrier and the conductive elastic roller are moved with a video microscope (OVM1000N manufactured by OLYMPUS) and a digital camera. Still recorder (SR-3100 made by DELTAS)
To shoot. With respect to the conductive elastic roller, the conductive elastic roller is brought into contact with the slide glass under the same conditions as those in contact with the image carrier.
Shoot more than points. In order to separate individual particles from the obtained digital image, binarization processing is performed with a certain threshold value, and the number of regions where particles are present is measured using desired image processing software. In addition, the abundance on the image carrier is measured by photographing the image carrier with the same video microscope and performing the same processing.

In the present invention, the conductive elastic roller member used as the contact charging member preferably has an Asker C hardness of 50 degrees or less. If the hardness is too low, the contact with the member to be charged is deteriorated because the shape is not stable,
Furthermore, by interposing conductive fine particles in the contact portion between the charging member and the image carrier, the surface layer of the roller member is shaved or damaged,
Stable chargeability cannot be obtained. On the other hand, if the hardness is too high, not only is it impossible to secure a charging contact portion with the member to be charged, but also the microscopic contact with the surface of the member to be charged deteriorates. Further, a preferred range is 25 to 50 degrees in Asker C hardness.

It is important that the roller member has elasticity to obtain a sufficient contact state with the member to be charged, and at the same time, functions as an electrode having a resistance low enough to charge the moving member to be charged. On the other hand, it is necessary to prevent voltage leakage when a defect site such as a pinhole is present in the member to be charged. When an electrophotographic photoreceptor is used as a member to be charged, the volume resistivity is preferably 1 × 10 ³ to 1 × 10 ⁸ Ωcm in order to obtain sufficient chargeability and leakage resistance. More preferably, the volume resistance value is 1 × 10 ⁴ to 1 × 10 ^7.
Ω · cm is good.

As for the volume resistance value of the roller member, 100 V is applied between the core metal and the aluminum drum while the roller is pressed against a cylindrical aluminum drum of φ30 mm so that a total pressure of 1 kg is applied to the core metal of the roller. Then, it can be measured by measuring.

The roller member according to the present invention can be produced, for example, by forming a medium-resistance layer of rubber or foam as a flexible member on a cored bar. The medium resistance layer is formulated with a resin (eg, urethane), conductive particles (eg, carbon black), a sulfide agent, a foaming agent, and the like, and is formed in a roller shape on a cored bar. Then, if necessary, the roller member can be prepared by cutting and polishing the surface to adjust the shape. The surface of the roller member preferably has minute cells or irregularities in order to interpose conductive fine particles.

This cell has an average cell diameter of 5 in spherical form.
It is preferred that the roller member has a dent of about 300 μm, and the porosity of the surface of the roller member having the dent as a gap is 15 to 90%.

When the average cell diameter on the surface of the roller member is smaller than 5 μm, the supply of the conductive fine particles becomes insufficient,
If it exceeds μm, the supply of the conductive fine particles becomes excessive, and in either case, the charging potential of the image carrier becomes uneven, which is not preferable. When the porosity is less than 50%, the supply of the conductive fine particles is insufficient, and when the porosity is more than 90%, the supply of the conductive fine particles becomes excessive, and the charging potential of the image carrier becomes non-uniform. Absent.

The material of the roller member is not limited to an elastic foam. Examples of the material of the elastic member include ethylene-propylene-diene polyethylene (EPDM), urethane, butadiene acrylonitrile rubber (NBR), silicone rubber, and isoprene. A rubber material in which a conductive substance such as carbon black or a metal oxide is dispersed in rubber or the like for resistance adjustment, or a material obtained by foaming the rubber material can be used. It is also possible to adjust the resistance by using an ion conductive material without dispersing the conductive material or in combination with the conductive material.

[0294] Examples of the core metal used for the roller member include aluminum and SUS.

The roller member is disposed in such a manner as to be pressed against a member to be charged as an image carrier against elasticity with a predetermined pressing force, and a charging contact portion which is a contact portion between the roller member and the image carrier is provided. A part is formed. The width of the charging contact portion is not particularly limited, but is preferably 1 mm or more, more preferably 2 mm or more in order to obtain a stable and close adhesion between the roller member and the image carrier.

Examples of the brush member as the contact charging member include a commonly used charging brush in which a conductive material is dispersed in fibers and the resistance is adjusted. As the fibers, generally known fibers can be used, and examples thereof include nylon, acrylic, rayon, polycarbonate, and polyester. As the conductive material, generally known conductive materials can be used, for example, conductive metals such as nickel, iron, aluminum, gold, and silver, or iron oxide, zinc oxide, tin oxide, antimony oxide, titanium oxide, and the like. And a conductive powder such as carbon black. In addition, these conductive materials may be subjected to a surface treatment for the purpose of hydrophobicity and resistance adjustment as required. At the time of use, it is selected and used in consideration of dispersibility with fibers and productivity.

When a charging brush is used as the contact charging member, there are a fixed type and a rotatable roll type. As the roll-shaped charging brush, for example, a tape in which conductive fibers are piled may be spirally wound around a metal core to form a roll brush. The conductive fiber has a fiber thickness of 1 to 20 denier (fiber diameter of 10 to 50).
The length of the brush fiber is 1 to 15 mm, and the brush density is 10,000 to 300,000 per square inch (about 1.5 × 10 ^{7 to} 4.5 × 10 ⁸ per square meter).
Is preferably used.

As the charging brush, it is preferable to use a brush having as high a brush density as possible, and it is also preferable to make one fiber from several to several hundreds of fine fibers. For example, 30
It is also possible to bundle 50 fine fibers of 300 denier, such as 0 denier / 50 filament, and to implant them as one fiber. However, in the present invention,
The charging point of direct injection charging is determined mainly by the charging contact portion between the charging member and the image carrier and the density of conductive fine particles in the vicinity thereof. The range has been widened.

The core used for the charging brush may be the same as that used for the charging roller member.

The volume resistance value of the charging brush is 1 × 1 to obtain sufficient charging properties and leakage resistance as in the case of the roller member.
The resistance is preferably from 0 ³ to 1 × 10 ⁸ Ω · cm, more preferably from 1 × 10 ⁴ to 1 × 10 ⁷ Ω · cm.

As the material of the charging brush, conductive rayon fibers REC-B and REC-B manufactured by Unitika Ltd. were used.
C, REC-M1, REC-M10, S manufactured by Toray Industries, Inc.
A-7, Thunderon manufactured by Nippon Silk Co., Ltd., Bertron manufactured by Kanebo Co., Ltd., Clacarbo manufactured by Kuraray Co., Ltd., a product obtained by dispersing carbon in rayon, Robal manufactured by Mitsubishi Rayon Co., Ltd. REC-B, RE in terms of stability
Particularly preferred are CC, REC-M1, and REC-M10.

Further, the fact that the contact charging member has flexibility increases the chance that the conductive fine particles come into contact with the image carrier at the contact portion between the contact charging member and the image carrier, and increases the contact property. Is preferable in that the direct injection charging property is improved. That is, the contact charging member comes into close contact with the image carrier via the conductive fine particles, and the conductive fine particles present at the contact portion between the contact charging member and the image carrier rub the surface of the image carrier without gaps. As a result, stable and safe direct injection charging without using a discharge phenomenon is dominant in the charging of the image carrier by the contact charging member due to the presence of the charging promoting particles, and high charging efficiency that cannot be obtained by conventional roller charging or the like is obtained. Thus, a potential substantially equal to the voltage applied to the contact charging member can be given to the image carrier.

Further, by providing a relative speed difference between the moving speed of the surface of the charging member forming the contact portion and the moving speed of the surface of the image carrier, the contact portion between the contact charging member and the image carrier is provided. This is preferable in that the opportunity for the conductive fine particles to come into contact with the image carrier is significantly increased, higher contact properties can be obtained, and the direct injection chargeability is improved.

The conductive fine particles are interposed in the contact portion between the contact charging member and the image carrier, and the lubricating effect (friction reduction effect) of the conductive fine particles greatly increases the distance between the contact charging member and the image carrier. Thus, it is possible to provide a speed difference without causing an excessive increase in torque and significant scraping of the contact charging member and the surface of the image carrier.

In order to temporarily collect the transfer residual toner on the image carrier carried to the charging section to the contact charging member and level it, the contact charging member and the image carrier move in opposite directions at the contact portion. It is preferable and preferable. For example, it is desirable that the contact charging member be driven to rotate, and that the rotation direction of the contact charging member be rotated in a direction opposite to the moving direction of the surface of the image carrier at the contact portion. That is, by directly separating the transfer residual toner on the image carrier by reverse rotation and performing charging, it is possible to perform superior direct injection charging.

Although the charging member can be moved in the same direction as the moving direction of the surface of the image carrier to have a speed difference, the chargeability of the direct injection charging depends on the peripheral speed of the image carrier and the peripheral speed of the charging member. In order to obtain the same peripheral speed ratio as in the reverse direction, the rotation speed of the charging member in the forward direction is larger than that in the reverse direction. This is advantageous.

As a configuration for providing a speed difference, a speed difference can be provided between the image carrier and the contact charging member by rotating the contact charging member. The peripheral speed ratio described here can be expressed by the following formula (IV) (the peripheral speed of the charging member is a positive value when the surface of the charging member moves in the same direction as the surface of the image carrier at the contact portion).

[0308]

## EQU4 ## Peripheral speed ratio (%) = (peripheral speed of charging member / peripheral speed of image carrier) × 100 Expression (IV) As an index indicating the relative speed difference, there is a relative moving speed ratio expressed by the following expression . Relative moving speed ratio (%) = | (Vc−Vp) / Vp | × 1
(Where Vc is the moving speed of the charging member surface, Vp is the moving speed of the image carrier surface, and Vc is Vc when the charging member surface moves in the same direction as the image carrier surface at the contact portion.
ptp has the same sign value. ) The relative moving speed ratio is usually 10 to 500%.

In order to temporarily collect the transfer residual toner on the image carrier, carry conductive fine particles, and perform superior direct injection charging, the conductive member, which is a flexible member as described above, is used as the contact charging member. It is preferable to use an elastic roller member or a rotatable charging brush roll.

In the image forming method of the present invention, the outermost layer of the image carrier has a volume resistivity of 1 × 10 ⁹ to 1 × 1.
When it is 0 ¹⁴ Ω · cm, better chargeability can be given, which is preferable. In the charging method by direct injection of electric charges, the electric charges can be transferred more efficiently by lowering the resistance of the photoreceptor which is the object to be charged. For this purpose, the volume resistivity of the outermost layer is 1 × 10 ¹⁴
It is preferable that the resistance is Ω · cm or less. On the other hand, in order to hold an electrostatic latent image as an image carrier for a certain period of time, the volume resistivity of the outermost surface layer is 1 × 10 ⁹ Ω · cm.
It is preferable that it is above.

Further, the image bearing member is an electrophotographic photosensitive member,
The volume resistance value of the outermost surface layer of the electrophotographic photosensitive member is 1 × 10 ⁹
It is more preferable that the average particle size is about 1 × 10 ¹⁴ Ω · cm, because sufficient chargeability can be provided even in an apparatus having a high process speed.

The image carrier is made of amorphous selenium, C
It is preferably a photosensitive drum or a photosensitive belt having a photoconductive insulating material layer such as dS, ZnO ₂ , amorphous silicon or an organic photosensitive material, and a photosensitive member having an amorphous silicon photosensitive layer or an organic photosensitive layer is particularly preferably used. Can be

In the present invention, the contact angle of water on the surface of the photoreceptor is preferably 85 degrees or more. In order to obtain such a photoreceptor, a polymer binder in which the surface of the photoreceptor is an organic photosensitive layer is used. An agent composed mainly of an agent and having a releasability can be used. For example, when a resin-based surface layer is provided on an inorganic photoreceptor such as selenium or amorphous silicon, or when a charge transport layer of a function-separated type photoreceptor has a surface layer composed of a charge transport material and a resin, Further, there is a case where the above-mentioned surface layer is provided thereon. Means for imparting releasability to such a surface layer include the following. (1) A resin having a low surface energy is used for the resin constituting the film. (2) Add an additive that imparts water repellency and lipophilicity. (3) A material having high releasability is powdered and dispersed in the resin.

As an example of (1), this can be achieved by introducing a fluorine-containing group, a silicone-containing group and the like into the structure of the resin. As (2), a surfactant or the like may be used as an additive. As the release powder as the material of (3), a compound containing a fluorine atom, that is, polytetrafluoroethylene,
Examples include polyvinylidene fluoride and carbon fluoride.

By these means, the contact angle of the surface of the photoreceptor with water can be made 85 degrees or more, and the transferability of the toner and the durability of the photoreceptor can be further improved. Preferably, it is 90 degrees or more. Among them, polytetrafluoroethylene is particularly preferable. In the present invention,
The means (3) for dispersing a releasable powder such as a fluorinated resin into the outermost surface layer is preferable. In this case, if the amount of the releasable powder added to the resin of the surface layer is increased, the contact angle with water can be increased.

The measurement of the contact angle is defined as the angle between the liquid surface and the surface of the photoreceptor (the angle inside the liquid) at the place where the free surface of water comes into contact with the photoreceptor by a drop-type contact angle meter.

The above measurement was performed at room temperature (about 21 to 25 ° C.)
It shall be performed in.

[0318] In order to incorporate the releasable powder on the surface,
Either providing a layer in which the releasable powder is dispersed in a binder resin on the outermost surface of the photoreceptor, or if the organic photoreceptor is originally composed mainly of resin, a new surface layer is not provided. Alternatively, the releasable powder may be dispersed in the uppermost layer. The addition amount is preferably 1 to 60% by mass, more preferably 2 to 50% by mass, based on the total mass of the surface layer. When the amount is less than 1% by mass, the effect of improving the transferability of the toner and the durability of the photosensitive member is insufficient. When the amount exceeds 60% by mass, the strength of the film is reduced, and the amount of light incident on the photosensitive member is significantly reduced. Is not preferred.

According to the present invention, the charging means contacts the charging member so as to form a contact portion with the photosensitive member as the image bearing member.
The direct charging method of charging the photoreceptor by applying a voltage is an essential component, but the load on the photoreceptor surface is larger than that of a method by corona discharge or the like in which the charging means does not contact the photoreceptor. In the above, it is more preferable that the photosensitive member has the following configuration instead of the above configuration.

As the organic photosensitive layer, the photosensitive layer may be a single layer type containing the same charge generating substance and charge transporting substance.
Alternatively, a photosensitive layer which may be a function-separated type photosensitive layer having a charge transport layer and a charge generation layer is used. That is, an organic photosensitive layer is provided on a conductive substrate, and a protective layer is provided on the surface thereof. A laminated photosensitive layer having a structure in which a charge generation layer and then a charge transport layer are laminated on a conductive substrate in this order is one of preferred examples.

Examples of the conductive substrate include metals such as aluminum and stainless steel, aluminum alloys and indium oxide.
Examples include cylindrical cylinders and films of plastic having a coating layer of a tin oxide alloy or the like, paper / plastic impregnated with conductive particles, plastic having a conductive polymer, and the like.

On these conductive substrates, improvement of adhesiveness of the photosensitive layer, improvement of coating properties, protection of the substrate, covering of defects on the substrate,
An undercoat layer may be provided for the purpose of improving the charge injection property from the substrate and protecting the photosensitive layer against electrical breakdown. The undercoat layer is polyvinyl alcohol, poly-N-vinyl imidazole, polyethylene oxide, ethyl cellulose,
It can be formed of materials such as methylcellulose, nitrocellulose, ethylene-acrylic acid copolymer, polyvinyl butyral, phenolic resin, casein, polyamide, copolymerized nylon, glue, gelatin, polyurethane, and aluminum oxide. The film thickness is usually 0.1 to 10
μm, preferably about 0.1 to 3 μm.

The charge generation layer is composed of an azo pigment, a phthalocyanine pigment, an indigo pigment, a perylene pigment, a polycyclic quinone pigment, a squarylium dye, a pyrylium salt, a thiopyrylium salt, a triphenylmethane dye,
It is formed by dispersing and applying a charge generating substance such as an inorganic substance such as amorphous silicon in a suitable binder resin, or by vapor deposition. As the binder resin used for the charge generation layer, a wide range of binder resins can be selected.For example, polycarbonate resin, polyester resin, polyvinyl butyral resin, polystyrene resin, acrylic resin, methacryl resin, phenol resin, silicone resin, epoxy resin Resins and vinyl acetate resins. The amount of the binder resin contained in the charge generation layer is 80% by mass or less, preferably 0 to 40% by mass. The thickness of the charge generation layer is 5 μm.
m, particularly preferably 0.05 to 2 μm.

[0324] The charge transport layer has a function of receiving charge carriers from the charge generation layer in the presence of an electric field and transporting them. The charge transporting layer is formed by dissolving a charge transporting substance in a solvent together with a binder resin if necessary, and applying the solution. The film thickness is generally 5 to 40 μm. As the charge transport material, biphenylene,
Anthracene, pyrene, polycyclic aromatic compounds having a structure such as phenanthrene, indole, carbazole, oxadiazole, nitrogen-containing cyclic compounds such as pyrazoline,
Hydrazone compounds, styryl compounds, selenium, selenium-
Tellurium, amorphous silicon, cadmium sulfide and the like. Examples of the binder resin for dispersing these charge transporting substances include resins such as polycarbonate resin, polyester resin, polymethacrylate, polystyrene resin, acrylic resin, and polyamide resin, and organic resins such as poly-N-vinylcarbazole and polyvinylanthracene. Photoconductive polymers and the like can be mentioned.

[0325] A protective layer may be provided as a surface layer. As the resin of the protective layer, polyester, polycarbonate,
An acrylic resin, an epoxy resin, a phenol resin, or a curing agent of these resins is used alone or in combination of two or more. It is preferable that conductive particles are dispersed in the resin of the protective layer. Examples of such conductive particles include metals, metal oxides and the like, preferably, zinc oxide, titanium oxide, tin oxide, antimony oxide, indium oxide, bismuth oxide, tin oxide coating titanium oxide, tin coating There are ultrafine particles of metal oxides such as indium oxide, antimony-coated tin oxide, and zirconium oxide. These may be used alone or as a mixture of two or more.

Further, it is preferable that lubricating fine particles are dispersed in the resin of the protective layer. As lubricating fine particles,
At least one selected from fluorine resin particles, silicone resin particles, and polyolefin resin particles is used.

Examples of the fluorine resin used for the lubricating fine particles include, for example, ethylene tetrafluoride resin, ethylene trifluoride resin, ethylene propylene hexafluoride resin, vinyl fluoride resin, vinylidene fluoride resin, A single resin or two or more resins can be appropriately selected from ethylene chloride resins and copolymers thereof.

Examples of the silicone resin used as the lubricating fine particles include KMP manufactured by Shin-Etsu Silicone Co., Ltd.
-590, X52-854, X52-821, X52-
830, X52-831 (silicone resin powder),
KMP110, KMP105, or the like can be used.

Examples of the polyolefin resin used as the lubricating fine particles include polyethylene and polypropylene resins. There is no particular limitation on the size of the lubricating fine particles.

In general, when particles are dispersed in a protective layer,
It is necessary that the particle diameter of the particles is smaller than the wavelength of the incident light in order to prevent scattering of the incident light by the dispersed particles, and the conductive particles dispersed in the protective layer in the present invention, the insulating lubricating fine particles. The particle size is preferably 0.5 μm or less. The content of these in the protective layer is preferably from 2 to 90% by mass relative to the total mass of the protective layer, and is preferably from 5 to 80% by mass.
% Is more preferred. The protective layer may also function as a charge injection layer.

The thickness of the protective layer is preferably from 0.1 to 10 μm, more preferably from 1 to 7 μm.

The resin layer is formed by laminating on the conductive substrate by vapor deposition or coating. Regarding the lamination method, specifically, a bar coater, a knife coater, a roll coater, an attritor, a spray, a dip coating, an electrostatic coating, a powder coating and the like are used for the coating. The coating method can be carried out by applying a solution or dispersion in which the constituent components of each layer are dissolved and dispersed in an organic solvent or the like by the above method, and then removing the solvent by drying or the like. Alternatively, when a reaction-curable binder resin is used, a solution or dispersion obtained by dissolving and dispersing each layer component in a resin raw material component and an appropriate organic solvent or the like added as necessary is used as described above. After applying by the method,
For example, the resin material may be reacted and cured by heat, light, or the like, and the solvent may be removed by drying or the like as necessary.

The organic solvent used for producing the photoreceptor includes ethanol, toluene, methyl ethyl ketone and the like.

In order to make the charge injection more efficient or promote by adjusting the surface resistance of the image carrier,
It is also preferable to provide a charge injection layer on the surface of the electrophotographic photosensitive member. The charge injection layer preferably has a form in which conductive particles are dispersed in a resin. Examples of the mode of providing the charge injection layer include (i) a case where the charge injection layer is provided on an inorganic photoreceptor such as selenium or amorphous silicon or a single layer type organic photoreceptor; In the case where the charge transport layer has a surface layer having a charge transport substance and a resin, and also has a function as a charge injection layer (for example, a charge transport substance and a conductive particle are dispersed in a resin as a charge transport layer, Alternatively, depending on the charge transport material itself or its existence state, the charge transport layer has a function as a charge injection layer), (iii) a case where a charge injection layer is provided as an outermost surface layer on the function-separated organic photoreceptor However, it is preferable that the volume resistance of the outermost surface layer is within the above range in the present invention. In this case, it is also possible to disperse the lubricating fine particles in the charge injection layer.

The charge injection layer is composed of, for example, an inorganic layer such as a metal vapor-deposited film, or a conductive powder-dispersed resin layer in which conductive particles are dispersed in a binder resin. The dispersed resin layer is formed by applying an appropriate coating method such as a dipping coating method, a spray coating method, a roll coating method, and a beam coating method. Further, a resin formed by mixing or copolymerizing an insulating binder resin with a resin having high light transmittance and ionic conductivity, or a resin formed of a single resin having a medium resistance and photoconductive properties may be used.

Of these, the outermost surface layer of the image carrier is preferably a resin layer in which the above-mentioned conductive fine particles made of a metal oxide are dispersed, whereby it is more efficient to lower the surface resistance of the electrophotographic photosensitive member. The transfer of charges can be carried out well, and the resistance of the surface is reduced while the electrostatic latent image is held as an image carrier. It is preferable in terms of suppression.

In the case of the conductive particle dispersion layer, the particle size of the particles needs to be smaller than the wavelength of the incident light in order to prevent scattering of the incident light by the dispersed particles. Is preferably 0.5 μm or less. The content of the conductive particles was 2 to the total weight of the outermost layer.
It is preferably from 90 to 90% by mass, more preferably from 5 to 70% by mass. When it is less than 2% by mass, it becomes difficult to obtain a desired volume resistance value, and when it is more than 90% by mass,
This is because the film strength is reduced, the charge injection layer is easily scraped off, the life of the photoreceptor tends to be shortened, and the resistance is reduced, and image defects are likely to occur due to the flow of a latent image potential. is there. Layer thickness is 0.1-10μ
m is preferable, and in order to obtain a sharp outline of the latent image, 5
μm or less, and more preferably 1 μm or more from the viewpoint of the durability of the charge injection layer. Further, the binder resin of the charge injection layer may be the same as the binder resin of the lower layer. In this case, the coating surface of the lower layer (for example, the charge transport layer) is disturbed when the charge injection layer is coated. Therefore, it is necessary to particularly select a forming method.

FIG. 8 is a schematic diagram showing the layer structure of a photoconductor provided with a charge injection layer as a surface layer. That is, the photosensitive member has a conductive layer 12 on a conductive substrate (aluminum drum substrate) 11.
Positive charge injection prevention layer 13, charge generation layer 14, charge transport layer 1
The charge performance is improved by applying the charge injection layer 16 to a general organic photoreceptor drum coated in the order of No. 5.

[0339] An important point as the charge injection layer 16 is that the surface layer of a volume resistivity in the range of ^{1 × 10 9 ~1 × 10 1} 4 Ω · cm. Even when the charge injection layer 16 is not provided as in the present configuration, for example, when the charge transport layer 15 is within the above-described resistance range, the same effect can be obtained. For example, even when an amorphous silicon photoreceptor having a surface layer having a volume resistance of about 10 ¹³ Ω · cm is used, good chargeability can be similarly obtained.

The method of measuring the volume resistivity of the outermost surface layer of the image bearing member according to the present invention is based on the same composition as that of the outermost surface layer of the image bearing member on a polyethylene terephthalate (PET) film having gold deposited on the surface. And a volume resistance measurement device (414 manufactured by Hewlett-Packard Company)
0BpAMATER) at 23 ° C and 65% environment.
A method of measuring by applying a voltage of 00V is exemplified.

Further, in the present invention, it is preferable to impart releasability to the surface of the image carrier, and the contact angle of water on the surface of the image carrier is preferably 85 degrees or more. More preferably, the contact angle of water on the surface of the image carrier is 90 degrees or more, as described above, and can be achieved by a similar method.

Next, the contact transfer step preferably applied in the image forming method of the present invention will be specifically described.

In the contact transfer step, the developed image is electrostatically transferred to the transfer material while the transfer means is in contact with the photoreceptor via the transfer material. It is preferably at least 9 N / m (3 g / cm), more preferably at least 19.6 N / m (20 g / cm). The linear pressure as the contact pressure is 2.9 N / m (3 g
/ Cm) is not preferable because transfer deviation of the transfer material and transfer failure are likely to occur.

As the transfer means in the contact transfer step, an apparatus having a transfer roller or a transfer belt is used. FIG. 4 shows an example of the configuration of the transfer roller. The transfer roller 34 includes at least the core metal 34 a and the conductive elastic layer 34.
b. The conductive elastic layer 34b is made of urethane or EPDM in which a conductive material such as carbon is dispersed, and has a volume resistance of 1 × 1.
0 ^6-1 is made of × ¹⁰ 10 Ω · cm about the elastic member, a transfer bias is applied by the transfer bias power source 35.

The image forming method of the present invention is particularly effective when the contact transfer method is used in an image forming apparatus in which the surface of the photoreceptor is an organic compound. That is, when the organic compound forms the surface layer of the photoreceptor, the adhesiveness with the binder resin contained in the toner particles is stronger than other photoreceptors using an inorganic material, and the transferability is further reduced. This is because there is a tendency to do so.

When the contact transfer method is applied to the image forming method of the present invention, the photoreceptor to be used is not particularly limited, but may be the above-described one.

Further, the image forming method of the present invention to which the contact transfer method is applied is particularly effectively used for an image forming apparatus having a small-diameter photosensitive member having a diameter of 50 mm or less. That is,
This is because, in the case of a small-diameter photosensitive member, the curvature for the same linear pressure is large, and the concentration of pressure at the contact portion is likely to occur. Although it is considered that the same phenomenon occurs in the belt photoconductor, the present invention is also effective for an image forming apparatus in which the radius of curvature at the transfer section is 25 mm or less.

In the present invention, the surface of the toner carrier for carrying the toner may move in the same direction as the moving direction of the surface of the image carrier, or may move in the opposite direction. Supply of toner particles and conductive fine particles from the toner carrier side to the image carrier side because the toner carrier that carries the toner in the process and conveys it to the developing unit with respect to the image carrier has a speed difference with respect to the image carrier. Is performed sufficiently, so that a good image can be obtained.

Specifically, with respect to the moving speed of the image carrier,
Desirably, it is 0.7 times or more. If it is less than 0.7 times, the image quality may be poor. The higher the moving speed ratio, the higher. The amount of toner supplied to the development site is large, the frequency of toner detachment from the latent image increases, and unnecessary parts are scraped off and applied to necessary parts repeatedly, so that an image faithful to the latent image is repeated. can get. Specifically, the moving speed of the toner carrier surface is preferably 0.7 to 3.0 times the moving speed of the image carrier surface, and more preferably 1.05 to 3.0 times. More preferably, the speed.

The surface roughness (Ra) of the toner carrier used in the present invention is preferably in the range of 0.2 to 3.5 μm in terms of JIS center line average roughness (Ra).

If Ra is less than 0.2 μm, the charge amount on the toner carrier becomes high, and the developability may be insufficient. If Ra exceeds 3.5 μm, the toner coat layer on the toner carrier may be uneven, resulting in uneven density on the image. More preferably, it is preferably in the range of 0.5 to 3.0 μm.

In the present invention, the surface roughness Ra of the toner carrier is determined by using a surface roughness measuring device (Surfcoder SE-30H, manufactured by Kosaka Laboratory Co., Ltd.) based on JIS surface roughness "JISB 0601". Corresponds to the center line average roughness measured. Specifically, a 2.5 mm portion as the measured length Ra is extracted from the roughness curve in the direction of its center line, the center line of the extracted portion is the X axis, the direction of the vertical magnification is the Y axis, and the roughness curve is When y = f (x), the value obtained by the following equation (V) is expressed in micrometer (μm).
We say what we expressed in.

[0353]

(Equation 5) The surface roughness (Ra) of the toner carrier in the present invention can be set in the above range by, for example, changing the polishing state of the surface layer of the toner carrier. That is, if the surface of the toner carrier is polished roughly, the surface roughness can be increased, and if the surface is polished finely, the surface roughness can be reduced. The surface roughness can also be adjusted by adding particles to a resin layer described later and adjusting the particle size and the amount of addition. The fine particles to be added refer to conductive fine particles described later, and organic and inorganic particles that are not completely compatible with the resin constituting the resin layer. The particle size is preferably from 0.005 to 10 μm.

As the toner carrier having the above-mentioned properties, there is a developing sleeve made of a non-magnetic metal such as aluminum or stainless steel as shown in FIG.

Further, since the magnetic toner according to the present invention has a high charging ability, it is desirable to control the total charge amount of the magnetic toner during development, and the surface of the toner carrier according to the present invention is It is preferable that the resin layer is covered with a resin layer in which conductive fine particles for a resin layer and / or a lubricant are dispersed.

In the coating layer of the toner carrier, the conductive fine particles contained in the resin material preferably have a resistance of 0.5 Ω · cm or less after being pressed at 120 kg / cm ² .

Examples of the conductive fine particles include carbon fine particles, a mixture of carbon fine particles and crystalline graphite,
Alternatively, crystalline graphite is preferred. The conductive fine particles preferably have a volume average particle diameter of 0.005 to 10 μm.

The resin material used for the resin layer on the surface of the toner carrier is, for example, a styrene resin, a vinyl resin,
Thermoplastic resins such as polyether sulfone resin, polycarbonate resin, polyphenylene oxide resin, polyamide resin, fluororesin, cellulose resin, acrylic resin; epoxy resin, polyester resin, alkyd resin, phenol resin, melamine resin, polyurethane resin, A thermosetting resin such as a urea resin, a silicone resin, and a polyimide resin or a photocurable resin can be used. Among them, silicone resin, those having a releasable property such as fluororesin, or polyether sulfone, polycarbonate, polyphenylene oxide, polyamide,
Those having excellent mechanical properties such as phenolic resins, polyesters, polyurethanes, and styrene resins are more preferable. Particularly, a phenol resin is preferable.

The conductive fine particles used for the resin layer on the surface of the toner carrier are 3 to 2 parts per 10 parts by mass of the resin component.
It is preferable to use 0 parts by mass. When carbon particles and graphite particles are used in combination, it is preferable to use 1 to 50 parts by mass of carbon particles per 10 parts by mass of graphite.

A sleeve tree in which conductive fine particles are dispersed
The volume resistivity of the fat coat layer is 1 × 10 ^-6~ 1 × 10⁶Ω
cm is preferred.

In the developing step of the present invention, it is preferable to form a toner layer of 5 to 50 g / m ² on the toner carrier. More preferably, the toner layer has a thickness of 5 to 40 g / m ² .

In the present invention, the fact that the member for regulating the toner on the toner carrier is brought into contact with the toner carrier via the toner is regulated so that the toner is hardly affected by the temperature and humidity environment. It is particularly preferable from the viewpoint of obtaining a uniform charge that does not easily cause toner scattering.

The toner layer thickness regulating member is particularly preferably regulated by an elastic member from the viewpoint of uniformly charging the magnetic toner.

In the image forming method of the present invention, in order to obtain high image quality without fogging, the closest distance between the toner carrier and the photosensitive member on the toner carrier (hereinafter also referred to as "between SD") is used. It is preferable that the development is performed in a development step of applying a magnetic toner with a small layer thickness and applying an AC electric field to perform development. That is, it is preferable that the toner layer thickness regulating member for regulating the magnetic toner on the toner carrier is set so that the closest gap between the photoconductor and the toner carrier is wider than the toner layer thickness on the toner carrier. .

Also, the toner carrier is one to the image carrier.
It is preferable that they are installed facing each other with a separation distance of 00 to 1000 μm. If the distance between the toner carrier and the image carrier is smaller than 100 μm, the change in the developing characteristic of the toner with respect to the fluctuation of the distance becomes large, and it is difficult to mass-produce an image forming apparatus satisfying stable image quality. Become. If the separation distance of the toner carrier from the image carrier is larger than 1000 μm, the ability of the toner to follow the latent image on the image carrier decreases, so that image quality such as resolution and image density decreases. May be invited.
Preferably, it is 120 to 500 μm.

In the present invention, it is preferable that the development is performed in a development step in which an AC electric field is applied to the toner carrier to perform development, but the applied development bias is obtained by superimposing an AC voltage (alternating voltage) on a DC voltage. Is also good.

As a waveform of the AC voltage, a sine wave, a rectangular wave, a triangular wave, or the like can be used as appropriate. Alternatively, a pulse wave formed by periodically turning on / off a DC power supply may be used. As described above, a bias whose voltage value periodically changes can be used as the waveform of the alternating voltage.

At least a peak-to-peak electric field strength of 3 × 10 ⁶ to 10 × 10 ⁶ V / m and a frequency of 100 to 50 are provided between the toner carrier and the image carrier for carrying the toner.
It is preferable to apply a 00 Hz AC electric field as a developing bias.

If the electric field strength of the developing bias applied between the toner carrier and the image carrier is smaller than 3 × 10 ⁶ V / m, the recoverability of the transfer residual toner to the developing device is reduced.
Fog due to poor collection is likely to occur. Further, since the developing power is small, an image having a low image density tends to be formed. On the other hand, if the electric field strength of the developing bias is larger than 10 × 10 ⁶ V / m, the developing power is too large, and the resolution is deteriorated due to the crushing of fine lines, and the image quality is easily deteriorated due to the increase in fog.
Image defects tend to occur due to leakage of the developing bias to the image carrier. The frequency of the AC component of the developing bias applied between the toner carrier and the image carrier is 100 Hz.
If it is smaller than this, the frequency of detachment of the toner from the latent image decreases, and the recovery of the transfer residual toner to the developing device tends to decrease, and the image quality tends to decrease. If the frequency of the AC component of the developing bias is higher than 5000 Hz, the amount of toner that can follow the change in the electric field is reduced, so that the recoverability of the transfer residual toner is reduced and the developability may be reduced.

Even if there is a high potential difference between the toner carrier and the image carrier due to application of an AC electric field as a developing bias or the like, charge injection into the image carrier by the developing unit does not occur. The conductive fine particles added therein are easily transferred to the image carrier side uniformly, and the conductive fine particles are uniformly applied to the image carrier, and uniform contact is made in the charging section, so that good chargeability can be obtained. .

In the present invention, the latent image forming means for forming an electrostatic latent image on the charged surface of the image carrier is preferably an image exposing means. The image exposure unit for forming an electrostatic latent image is not limited to a laser scanning exposure unit for forming a digital latent image, but may be a normal analog image exposure or another light emitting element such as an LED. It does not matter if an electrostatic latent image corresponding to image information can be formed, such as a combination of a light emitting element such as a fluorescent lamp and a liquid crystal shutter.

The image carrier may be an electrostatic recording dielectric or the like. In this case, the dielectric surface is uniformly charged to a predetermined polarity / potential, and then selectively neutralized by a static elimination means such as a static elimination needle head or an electron gun to write and form a target electrostatic latent image.

In the present invention, in order to apply the non-contact developing method, it is preferable that the toner layer on the toner carrier is formed thinner than the separation distance of the toner carrier from the image carrier. In the development step, the non-contact type developing method of visualizing an electrostatic latent image of the image carrier as a toner image by applying a non-contact state of the toner layer to the image carrier is used to remove conductive fine particles having a low electric resistance value. Even if it is added to the toner, development fog due to injection of the development bias into the image carrier does not occur. Therefore, a good image can be obtained.

In the toner of the present invention, the particle size distribution of the magnetic material is uniform, so that the dispersibility of the magnetic material is uniform and good. Further, the shape and surface properties of the toner are uniform. From these facts, the charging speed and the charging amount distribution of the toner are uniform, and the transfer residual toner is small. When the toner of the present invention is applied to the above-described image forming method, the transfer residual toner is small, and the transfer residual toner is quickly charged when passing through the charging portion, and is quickly collected or developed by the toner carrier. . In addition, the adhesive force with the conductive fine particles is easily controlled appropriately due to the shape, and is more effectively supplied to the charging portion.

[0375]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Production Examples and Examples, but this does not limit the present invention in any way. All parts in the following formulations are parts by mass.

The evaluation method used in the examples is as follows. (1) Toner circularity and mode circularity About 5 mg of toner is dispersed in 10 ml of water in which about 0.1 mg of a surfactant is dissolved, and a dispersion is prepared.
z, 50 W) to the dispersion for 5 minutes to bring the dispersion concentration to 50
The average circularity and the mode circularity of the toner were determined by using a flow-type particle image analyzer FPIA-1000 manufactured by TOA MEDICAL ELECTRONICS CO., LTD. (2) Ratio of iron element content (B) to carbon element content (A) present on toner surface (B / A) Iron element content to carbon element content (A) present on toner surface The ratio (B / A) of the quantity (B) is ESCA (X
(Line photoelectron spectroscopy) to calculate the surface composition. In the present invention, the ESCA apparatus and measurement conditions are as follows. Apparatus used: 1600S type X-ray photoelectron spectrometer manufactured by PHI Measurement conditions: X-ray source MgKα (400 W) Spectral region 800 μmφ In the present invention, PH is determined from the measured peak intensity of each element.
The surface atomic concentration was calculated using the relative sensitivity factor provided by Company I. (3) D / C value of toner For a toner particle for determining D / C by TEM, an equivalent circle diameter is determined from a cross-sectional area in a micrograph, and the value is a width of ± 10% of a number average particle diameter. And the minimum value (D) of the distance between the surface of the magnetic substance and the surface of the magnetic toner particle is measured for the relevant toner particle.
Calculate C. The D / C value thus calculated is 0.02
The following ratio of the magnetic toner particles is defined to be determined by the following formula (III). The micrograph at this time is preferably at a magnification of 10,000 to 20,000 times in order to perform highly accurate measurement. In the present invention, a transmission electron microscope (H-600 manufactured by Hitachi, Ltd.) is used.
Observation at an accelerating voltage of 100 kV using
Observation / measurement was performed using a microphotograph with a magnification of 10,000 times.

[0377]

(Equation 6) (4) Particle Size of Toner In this example, the weight average particle size of the toner was determined as follows. Using a Coulter Multisizer (manufactured by Coulter), an interface (manufactured by Nikkaki) for outputting the number distribution and volume distribution and a PC9801 personal computer (manufactured by NEC) were connected, and the electrolyte was 1% NaCl using primary sodium chloride. Prepare the aqueous solution. As a measurement method, 0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant to 100 to 150 ml of the aqueous electrolytic solution, and 2 to 20 mg of a measurement sample is further added. The electrolytic solution in which the sample was suspended was subjected to dispersion treatment for about 1 to 3 minutes using an ultrasonic disperser, and the volume and number of toner particles having a size of 2 μm or more were measured using the Coulter Multisizer with a 100 μm aperture as the aperture. And the number distribution were calculated. Then, the volume-based weight average particle diameter (D4) and volume average particle diameter (DV) determined from the volume distribution according to the present invention, the number-based length average particle diameter determined from the number distribution, that is, the number average particle diameter (D) D1) was determined. (5) Volume Average Particle Size and Particle Size Distribution of Magnetic Material The volume average particle size and particle size distribution of the magnetic material are determined by the following measuring methods. In a state where the particles are sufficiently dispersed, the projected area of each of the 100 magnetic particles in the visual field is measured with a transmission electron microscope (TEM) at a magnification of 30,000 times, and each measured magnetic field is measured. The equivalent diameter of a circle equal to the projected area of the body particles was determined as each magnetic body particle diameter. Further, based on the results, the number% of particles of 0.03 to 1 μm and particles of 0.3 μm or more were calculated. Also,
It is also possible to measure the particle size with an image analyzer.

In determining the volume average particle size and the particle size distribution of the magnetic substance in the toner particles, the following measuring methods are used.

After sufficiently dispersing the toner particles to be observed in the epoxy resin, the cured product obtained by curing for 2 days in an atmosphere at a temperature of 40 ° C. is obtained as a flaky sample by a microtome, and is observed by a transmission electron microscope. In (TEM), the projected area of each of the 100 magnetic particles in the field of view was measured with a photograph at a magnification of 10,000 to 40,000 times, and the equivalent diameter of a circle equal to the measured projected area of each magnetic particle was measured. Was determined as the particle diameter of each magnetic substance. Further, based on the result, 0.03
The number% of particles of 0.1 μm and particles of 0.3 μm or more were calculated. Further, the particle size can be measured by an image forming apparatus. (6) True Density and Bulk Density of Magnetic Body The true density of the magnetic body was determined using Micromeritics Acupic 1330 (manufactured by Shimadzu Corporation). The bulk density of the magnetic material is JIS (Japanese Industrial Standard) K-5101 (1
991). (7) Method for Measuring Content of Complex Oxide in Toner The content of complex oxide in the toner was measured with a thermal analyzer TGA7 manufactured by PerkinElmer. The measuring method is as follows.
The toner was heated to 0 ° C., and the weight loss% between 100 ° C. and 750 ° C. was defined as the binder resin amount. Total toner (10
0 mass%), and the remainder obtained by subtracting the amount of the binder resin was approximately used as the content of the composite oxide in the toner. <1> Production of Magnetic Body Magnetic bodies 1 ′ to 4 ′ for comparison with magnetic bodies 1 to 10 were obtained as follows. <Production of magnetic substance 1> In an aqueous solution of ferrous sulfate, l. An aqueous solution containing ferrous hydroxide was prepared by mixing 0 to 1.1 equivalents of a sodium hydroxide solution and sodium silicate.

While maintaining the pH of the aqueous solution at around 9, empty
And oxidize at 80-90 ° C to form seed crystals.
A slurry liquid to be produced was prepared. Then, this slurry
-The initial amount of alkali (sodium in caustic soda)
Ferrous sulfate water in an amount of 0.9 to 1.2 equivalents to
After the solution has been added, the slurry is maintained at pH 8 and air
Promotes the oxidation reaction while blowing
The magnetic iron oxide particles were washed, filtered, and once taken out. This
At this time, collect a small amount of water-containing sample and measure the water content.
Was. Next, the wet sample is dried without drying in another aqueous medium.
After redispersion, the pH of the redispersion is adjusted to about 6,
The silane coupling agent (n-C_TenH_{twenty one}
Si (OCH_Three)_Three) Is 1.2 parts by mass based on the magnetic iron oxide.
(The amount of magnetic iron oxide is the value obtained by subtracting the water content from the water-containing sample.
And the coupling treatment was performed.
Next, we will perform classification by wet classification using precipitation separation.
Hydrophobic iron oxide particles obtained by further removing fine particle components
Is washed, filtered, dried in a conventional manner, and then slightly aggregated.
The magnetic particles 1 were obtained by crushing the particles. <Manufacture of magnetic body 1 ′> Oxidation reaction in the same manner as manufacture of magnetic body 1
To wash the magnetic iron oxide particles generated after the oxidation reaction,
After filtration, without surface treatment, wet fractionation using precipitation separation
The fine particles are removed by classification using a classification method.
Dried and agglomerated particles are crushed, and magnetic material for comparison
1 'was obtained. <Manufacture of Magnetic Body 2> The above-mentioned magnetic body 1 ′ was newly prepared with water.
After redispersion in the system medium, adjust the pH of the redispersed liquid to about 6.
Silane coupling agent (n-C
_TenH_{twenty one}Si (OCH_Three)_Three) Is 1.2 quality for magnetic iron oxide
An amount was added and a coupling treatment was performed. Next, the sediment
Particles are classified by wet classification using separation.
And remove the resulting hydrophobic iron oxide particles by a standard method.
Wash, filter and dry, then crush the aggregated particles.
Thus, a magnetic material 2 was obtained. <Manufacture of magnetic body 3>
The pulling agent is (n-C₆H₁₁Si (OCH_Three)_Three)
A magnetic body 3 was obtained in the same manner as in the manufacture of the magnetic body 1 except for the above. <Manufacture of magnetic body 4>
The pulling agent (n-C₁₈H₃₇Si (OCH _Three)_Three)
Except for the above, a magnetic body 4 was obtained in the same manner. <Production of Magnetic Materials 5 to 9>
Ferrous aqueous solution concentration, sodium silicate concentration, air blowing
Volume, agitation speed and pH of the solution during production
Sex bodies 5 to 9 were obtained. <Manufacture of magnetic body 10> In the manufacture of magnetic body 1, sulfuric acid
Ferrous aqueous solution concentration, sodium silicate concentration, air blowing amount,
Change the wet classification by changing the stirring speed and the pH of the liquid during production.
Do not perform the same procedure except that the fine particle components are not removed.
Was obtained, and a magnetic body 10 was obtained in the same manner as the magnetic body 2. <Production of Magnetic Materials 2 ′ to 4 ′> In the production of the magnetic material 1,
Ferrous sulfate aqueous solution concentration, sodium silicate concentration, air blowing
Volume, stirring speed and the pH of the liquid at the time of production are appropriately changed,
Magnetic materials 2 'to 4' for comparison were obtained. These magnets obtained
Table 1 shows typical physical property values of the sex compounds.

[0381]

[Table 1] <2> Production of conductive fine particles Conductive fine particles 1 to 4 were obtained as follows. <Conductive Fine Particle 1> Fine particle zinc oxide having a volume average particle size of 3.5 μm, 6.8 volume% of 0.5 μm or less in the particle size distribution, and 7 number% of 5 μm or more (resistance 70 Ω · cm, volume average primary particle size 0) The obtained zinc oxide primary particles having a particle size of 0.1 to 0.3 μm were granulated by pressure (white) to obtain conductive fine particles 1.

The conductive fine particles 1 were observed with a scanning electron microscope at 3,000 and 30,000 times,
It consisted of zinc oxide primary particles of 0.3 μm and aggregates of 1 to 10 μm.

An exposure wavelength 740 of a laser beam scanner used for image exposure in an image forming apparatus according to the first embodiment described later.
When the transmittance in this wavelength range was measured using a 310T transmission densitometer manufactured by X-Rite, using a light source having a wavelength of 740 nm, the transmittance of the conductive fine particles 1 was about 35%. Was. <Conductive Fine Particle 2> A volume average particle diameter of 1.3 μm, obtained by classifying the conductive fine powder 1 by wind power, and a 0.1 μm particle size distribution.
Fine particle zinc oxide with 40 volume% for 5 μm or less and 0 number% for 5 μm or more (resistance 1400 Ω · cm, transmittance 35%)
Are conductive fine particles 2.

When the conductive fine particles 2 were observed with a scanning electron microscope, they consisted of zinc oxide primary particles of 0.1 to 0.3 μm and aggregates of 1 to 4 μm. By comparison, the primary particles were increasing. <Conductive Fine Particle 3> A volume average particle diameter of 2.4 μm, obtained by classifying the conductive fine powder 1 by wind force, and a particle size distribution of 0.2 μm.
Fine particle zinc oxide (resistance: 500 Ω · cm, transmittance: 35%) having a volume of 5% or less of 4.1% by volume and a size of 5 μm or more of 1% by volume is defined as the conductive particles 3.

When the conductive fine particles 3 were observed with a scanning electron microscope, they were composed of 0.1-0.3 μm zinc oxide primary particles and 1-5 μm aggregates. By comparison, the primary particles were reduced. <Conductive Fine Particles 4> After removing coarse particles by a wind classification, aluminum borate having a volume average particle diameter of 2.6 μm surface-treated with tin oxide / antimony is dispersed in an aqueous system and repeatedly subjected to filtration to obtain fine particles. Except for the volume average particle diameter of 3.0 μm, and 0.5 μm or less in the particle size distribution
Gray-white conductive particles having a volume percentage of 5% or more and 1% by number were obtained. This is referred to as conductive fine particles 4.

Table 2 shows typical physical property values of the conductive fine particles 1 to 4.
Shown in

[0387]

[Table 2] <3> Production of Magnetic Toner Magnetic toners A to Q, X to Z, and a to
c, and magnetic toners R to W were obtained for comparison. <Production of Magnetic Toner A> 450 parts by mass of a 0.1 M Na ₃ PO ₄ aqueous solution was added to 710 parts by mass of ion-exchanged water, and
After warming to ° C, 67.7 aqueous 1.0 M CaCl ₂ solution.
Parts by mass were gradually added to obtain an aqueous solution of calcium phosphate. The following materials were uniformly dispersed and mixed using a TK homomixer (Tokuki Kika Kogyo Co., Ltd.) to obtain a monomer composition.

Styrene: 80 parts by mass n-butyl acrylate: 20 parts by mass Unsaturated polyester resin: 2 parts by mass Saturated polyester resin: 4 parts by mass Load control agent (monoazo Dye-based Fe compound) ^*) 1 part by mass Magnetic substance 1 ... 100 parts by mass *) The monoazo dye-based Fe compound used here is a compound represented by the following general formula (III).

[0389]

Embedded image The monomer composition was heated to 60 ° C., and 8 parts by mass of an ester wax mainly composed of behenyl behenate (maximum endothermic peak in DSC of 72 ° C.) was added thereto, mixed and dissolved, and a polymerization initiator was added thereto. 4 parts by mass of 2,2′-azobis (2,4-dimethylvaleronitrile) was dissolved.

The above-mentioned polymerizable monomer system was charged into the above-mentioned aqueous medium, and the mixture was heated at 10,000 rpm with a TK-type homomixer (Special Kika Kogyo Co., Ltd.) at 65 ° C. under a nitrogen atmosphere.
The mixture was stirred for 5 minutes and granulated. Thereafter, the mixture was reacted at 65 ° C. for 6 hours while stirring with a paddle stirring blade. After that, the liquid temperature was 80 ° C.
The stirring was further continued for 4 hours. After completion of the reaction, distillation was carried out at 80 ° C. for further 2 hours. Thereafter, the suspension was cooled, hydrochloric acid was added to dissolve the calcium phosphate salt, filtered, washed with water and dried to obtain a magnetic toner having a weight average particle size of 6.6 μm. Particle A was obtained.

100 parts by mass of the magnetic toner particles A and 1.1 parts by mass of fine silica particles having a number average primary particle diameter of 7 nm and treated with hexamethyldisilazane to obtain a BET value of 250 m ² / g. Were mixed with a Henschel mixer (Mitsui Miike Kakoki Co., Ltd.) to prepare Magnetic Toner A. Table 3 shows the physical properties of Magnetic Toner A. <Production of Magnetic Toner B> Magnetic toner particles B having a weight average particle diameter of 6.5 μm were obtained in the same manner as in the production of magnetic toner particles A.

100 parts by mass of the magnetic toner particles B and silica having a primary particle diameter of 12 nm were treated with hexamethyldisilazane, and then treated with silicone oil. After the treatment, a hydrophobic silica fine powder having a BET value of 130 m ² / g was prepared. 1 part by mass was mixed with a Henschel mixer (Mitsui Miike Kakoki Co., Ltd.) to prepare Magnetic Toner B. Table 3 shows the physical properties of Magnetic Toner B. <Production of Magnetic Toner C> In the production of the magnetic toner particles A, the magnetic toner particles C having a weight average particle diameter of 5.3 μm were prepared by the same method except that 100 parts by mass of the magnetic material 2 was used instead of the magnetic material 1. Obtained. 100 parts by mass of the magnetic toner C particles and 1.1 parts by mass of silica fine powder treated with hexamethyldisilazane used in the production of the magnetic toner B were mixed with a Henschel mixer (Mitsui Miike Koki Co., Ltd.). Thus, a magnetic toner C was prepared. Table 3 shows the physical properties of Magnetic Toner C. <Production of Magnetic Toner D> In the production of the magnetic toner particles A, the magnetic toner particles D having a weight average particle diameter of 6.6 μm were prepared in the same manner except that 100 parts by mass of the magnetic material 3 was used instead of the magnetic material 1. Obtained. 100 parts by mass of the magnetic toner particles D and 1.1 parts by mass of the hydrophobic silica fine powder used in the production of the magnetic toner B are mixed with a Henschel mixer (Mitsui Miike Kakoki Co., Ltd.) to prepare a magnetic toner D. did. Table 3 shows the physical properties of Magnetic Toner D. <Production of Magnetic Toner E> In the production of the magnetic toner particles A, the magnetic toner particles E having a weight average particle size of 7.3 μm were prepared in the same manner except that 100 parts by mass of the magnetic material 4 was used instead of the magnetic material 1. Obtained. 100 parts by mass of the magnetic toner particles E and 1.1 parts by mass of the hydrophobic silica fine powder used in the production of the magnetic toner B were mixed with a Henschel mixer (Mitsui Miike Kakoki Co., Ltd.) to prepare a magnetic toner E. did. Table 3 shows the physical properties of the magnetic toner E. <Production of Magnetic Toner F> In the production of the magnetic toner particles A, the magnetic toner particles F having a weight average particle diameter of 5.9 μm were prepared in the same manner except that 100 parts by mass of the magnetic material 5 was used instead of the magnetic material 1. Obtained. The magnetic toner F is prepared by mixing 100 parts by mass of the magnetic toner particles F and 1.1 parts by mass of the hydrophobic silica fine powder used in the production of the magnetic toner B with a Henschel mixer (Mitsui Miike Koki Co., Ltd.). did. Table 3 shows the physical properties of Magnetic Toner F. <Production of Magnetic Toner G> In the production of the magnetic toner particles A, the magnetic toner particles G having a weight average particle diameter of 7.8 μm were produced in the same manner except that 100 parts by mass of the magnetic material 6 was used instead of the magnetic material 1. Obtained. A magnetic toner G is prepared by mixing 100 parts by weight of the magnetic toner particles G and 1.1 parts by weight of the hydrophobic silica fine powder used in the production of the magnetic toner B with a Henschel mixer (Mitsui Miike Kakoki Co., Ltd.). did. Table 3 shows the physical properties of Magnetic Toner G. <Production of Magnetic Toner H> In the production of the magnetic toner particles A, 100 parts by mass of the magnetic material 7 was used in place of the magnetic material 1,
By the same method except that the wax is polyethylene wax (the maximum endothermic peak in DSC is 115 ° C),
Magnetic toner particles H having a weight average particle size of 6.5 μm were obtained. 100 parts by mass of the magnetic toner particles A and 1.1 parts by mass of the hydrophobic silica fine powder used in the production of the magnetic toner B were mixed with a Henschel mixer (Mitsui Miike Kakoki Co., Ltd.),
Magnetic toner H was prepared. Table 3 shows the physical properties of Magnetic Toner H. <Production of Magnetic Toner I> In the production of the magnetic toner particles A, a magnetic toner particle I having a weight average particle diameter of 8.1 μm was prepared by the same method except that 100 parts by mass of the magnetic substance 8 was used instead of the magnetic substance 1. Obtained. 100 parts by mass of the magnetic toner particles I and 1.1 parts by mass of the hydrophobic silica fine powder used in the production of the magnetic toner B were mixed with a Henschel mixer (Mitsui Miike Kakoki Co., Ltd.) to prepare a magnetic toner I. did. Table 3 shows the physical properties of Magnetic Toner I. <Production of Magnetic Toner J> In the production of the magnetic toner particles A, the magnetic toner particles J having a weight average particle diameter of 9.0 μm were produced by the same method except that 100 parts by mass of the magnetic substance 9 was used instead of the magnetic substance 1. Obtained. A magnetic toner J is prepared by mixing 100 parts by weight of the magnetic toner particles A and 1.1 parts by weight of the hydrophobic silica fine powder used in the production of the magnetic toner B with a Henschel mixer (Mitsui Miike Kakoki Co., Ltd.). did. Table 3 shows the physical properties of Magnetic Toner J. <Production of Magnetic Toner K> In the production of the magnetic toner particles A, a magnetic toner particle K having a weight average particle diameter of 6.6 μm was produced by the same method except that 100 parts by mass of the magnetic substance 10 was used instead of the magnetic substance 1. Obtained. The magnetic toner particles K100
The magnetic toner K was prepared by mixing parts by mass and 1.1 parts by mass of the hydrophobic silica fine powder used in the production of the magnetic toner B with a Henschel mixer (Mitsui Miike Kakoki Co., Ltd.).
Table 3 shows the physical properties of Magnetic Toner K. <Production of Magnetic Toner L> In the production of the magnetic toner particles A, the amounts of the aqueous Na ₃ PO ₄ solution and the CaCl ₂ aqueous solution were changed to obtain magnetic toner particles L having a weight average particle diameter of 4.1 μm. 100 parts by mass of the magnetic toner particles L and 1.8 parts by mass of the hydrophobic silica fine powder used in the production of the magnetic toner B were mixed with a Henschel mixer (Mitsui Miike Kakoki Co., Ltd.) to prepare a magnetic toner L. did. Table 3 shows the physical properties of Magnetic Toner L. <Production of Magnetic Toner M> In the production of the magnetic toner particles A, the amounts of the aqueous Na ₃ PO ₄ solution and the aqueous CaCl ₂ solution were changed, and the ester wax was changed to paraffin wax (D
The maximum value of the endothermic peak in SC was 46 ° C.) to obtain magnetic toner particles M having a weight average particle size of 9.8 μm. 100 parts by mass of the magnetic toner particles M and 1.0 part by mass of the hydrophobic silica fine powder used in the production of the magnetic toner B were mixed with a Henschel mixer (Mitsui Miike Kakoki Co., Ltd.) to prepare a magnetic toner M. did. Table 3 shows the physical properties of the magnetic toner M. <Production of Magnetic Toner N> Magnetic toner particles N having a weight average particle size of 5.8 μm were obtained in the same manner as in the production of magnetic toner particles A except that the amount of the ester wax was changed to 55 parts by mass. The magnetic toner N is prepared by mixing 100 parts by mass of the magnetic toner particles N and 1.1 parts by mass of the hydrophobic silica fine powder used in the production of the magnetic toner B with a Henschel mixer (Mitsui Miike Kako Co., Ltd.). did. Table 3 shows the physical properties of the magnetic toner N. <Production of Magnetic Toner O> In the production of the magnetic toner particles A, magnetic toner particles O having a weight average particle diameter of 7.2 μm were obtained by the same method except that the amount of the ester wax used was changed to 0.3 parts by mass. . 100 parts by mass of the magnetic toner particles O and 1.1 parts by mass of the hydrophobic silica fine powder used in the production of the magnetic toner B are mixed by a Henschel mixer (Mitsui Miike Kakoki Co., Ltd.) to prepare a magnetic toner O. did. Table 3 shows the physical properties of Magnetic Toner O. <Production of Magnetic Toner P> In the production of the magnetic toner particles A, magnetic toner particles P having a weight average particle diameter of 7.1 μm were obtained by the same method except that the amount of the magnetic material 1 was changed to 55 parts by mass. 100 parts by mass of the magnetic toner particles P and 1.1 parts by mass of the hydrophobic silica fine powder used in the production of the magnetic toner B were mixed with a Henschel mixer (Mitsui Miike Kakoki Co., Ltd.)
To prepare a magnetic toner P. Table 3 shows the physical properties of the magnetic toner P. <Production of Magnetic Toner Q> In the production of the magnetic toner particles A, magnetic toner particles Q having a weight average particle diameter of 6.8 μm were obtained by the same method except that the amount of the magnetic material 1 was changed to 145 parts by mass. 100 parts by mass of the magnetic toner particles Q and the hydrophobic silica fine powder 1.1 used in the production of the magnetic toner B
Parts by mass were mixed with a Henschel mixer (Mitsui Miike Kakoki Co., Ltd.) to prepare Magnetic Toner Q. Table 3 shows the physical properties of the magnetic toner Q. <Production of Magnetic Toner R> In the production of the magnetic toner particles A, the magnetic toner particles R having a weight average particle size of 3.9 μm were produced in the same manner except that 100 parts by mass of the magnetic material 1 ′ was used instead of the magnetic material 1. I got This magnetic toner particle R100
The magnetic toner R was prepared by mixing 2.0 parts by mass of the hydrophobic silica fine powder used in the production of the magnetic toner B with a Henschel mixer (Mitsui Miike Koki Co., Ltd.).
Table 3 shows the physical properties of the magnetic toner R. <Production of Magnetic Toner S> In the production of the magnetic toner particles A, the magnetic toner particles S having a weight average particle diameter of 6.9 μm were produced in the same manner except that 100 parts by mass of the magnetic substance 2 ′ was used instead of the magnetic substance 1. I got The magnetic toner particles S100
And 1.1 parts by mass of the hydrophobic silica fine powder used in the production of the magnetic toner B were mixed with a Henschel mixer (Mitsui Miike Kakoki Co., Ltd.) to prepare a magnetic toner S. Table 3 shows the physical properties of the magnetic toner S. <Production of Magnetic Toner T> In the production of the magnetic toner particles A, a magnetic toner particle T having a weight average particle diameter of 8.8 μm was produced in the same manner except that 100 parts by mass of the magnetic substance 3 ′ was used instead of the magnetic substance 1. I got The magnetic toner particles T100
And 1.1 parts by mass of the hydrophobic silica fine powder used in the production of the magnetic toner B were mixed with a Henschel mixer (Mitsui Miike Kakoki Co., Ltd.) to prepare a magnetic toner T. Table 3 shows the physical properties of the magnetic toner T. <Production of Magnetic Toner U> In the production of the magnetic toner particles A, the magnetic toner particles U having a weight average particle diameter of 5.9 μm were produced in the same manner except that 100 parts by mass of the magnetic substance 3 ′ was used instead of the magnetic substance 1. I got The magnetic toner particles U100
And 1.1 parts by mass of the hydrophobic silica fine powder used in the production of the magnetic toner B were mixed with a Henschel mixer (Mitsui Miike Kakoki Co., Ltd.) to prepare a magnetic toner U. Table 3 shows the physical properties of the magnetic toner U. <Production of Magnetic Toner V> The following materials were mixed in a blender, melted and kneaded in a biaxial extruder heated to 110 ° C., and the cooled kneaded material was roughly pulverized by a hammer mill, and the coarsely pulverized product was finely pulverized by a jet mill. After the pulverization, the obtained finely pulverized product is classified by wind power to obtain magnetic toner particles V having a weight average particle size of 9.1 μm.
I got

Styrene / n-butyl acrylate copolymer: 100 parts by mass (mass ratio 80/20) Unsaturated polyester resin: 2 parts by mass Saturated polyester resin: 4 parts by mass Load control agent (monoazo dye type Fe ^compound) of *) .... 3 parts by magnetic substance 1 ... 90 parts by mass ester wax .... 6 parts by weight used in the manufacture of magnetic toner a *) monoazo dye The Fe compound is a compound represented by the general formula (III). A mixture obtained by adding 1.0 part by mass of the hydrophobic colloidal silica used in the production of the magnetic toner A to 100 parts by mass of the magnetic toner particles V was mixed with a Henschel mixer to prepare a magnetic toner V. Table 3 shows the physical properties of the magnetic toner V. <Production of Magnetic Toner W> Magnetic toner particles W were obtained in the same manner as in the production of magnetic toner particles U, except that the coarsely pulverized product was finely pulverized with a turbo mill (manufactured by Turbo Industries, Ltd.). Thereafter, spherical magnetic toner particles W ′ having a weight average particle size of 7.8 μm were obtained using an impact type surface treatment apparatus (treatment temperature: 50 ° C., peripheral speed of a rotary treatment blade: 90 m / sec.).

Next, the obtained spherical magnetic toner particles W ′
A mixture obtained by adding 1.0 part by mass of the hydrophobic colloidal silica used in the production of the magnetic toner B to 100 parts by mass was mixed with a Henschel mixer to prepare a magnetic toner W. Table 3 shows the physical properties of the magnetic toner W. <Production of Magnetic Toner X> Magnetic toner particles X having a weight average particle size of 6.4 μm were obtained in the same manner as in the production of magnetic toner particles A. 100 parts by mass of the magnetic toner particles X and the hydrophobic colloidal silica used in the production of the magnetic toner B
Magnetic toner X was prepared by mixing 1 part by mass and 2.0 parts by mass of conductive fine particles 1 with a Henschel mixer (Mitsui Miike Kakoki Co., Ltd.). Table 3 shows the physical properties of Magnetic Toner X. <Production of Magnetic Toner Y> Magnetic toner particles Y having a weight average particle diameter of 6.5 μm were obtained in the same manner as in the production of magnetic toner particles A. 100 parts by mass of the magnetic toner particles Y and the hydrophobic colloidal silica used in the production of the magnetic toner B
Magnetic toner Y was prepared by mixing 1 part by mass and 2.0 parts by mass of conductive fine particles 2 with a Henschel mixer (Mitsui Miike Kakoki Co., Ltd.). Table 3 shows the physical properties of the magnetic toner Y. <Production of Magnetic Toner Z> Magnetic toner particles Z having a weight average particle diameter of 6.5 μm were obtained in the same manner as in the production of magnetic toner particles A. 100 parts by mass of the magnetic toner particles Z and the hydrophobic colloidal silica used in the production of the magnetic toner B
Magnetic toner Z was prepared by mixing 1 part by mass and 2.0 parts by mass of conductive fine particles 3 with a Henschel mixer (Mitsui Miike Kakoki Co., Ltd.). Table 3 shows the physical properties of Magnetic Toner Z. <Production of Magnetic Toner a> Magnetic toner particles a having a weight average particle diameter of 6.4 μm were obtained in the same manner as in the production of the magnetic toner particles A. 100 parts by mass of the magnetic toner particles a and the hydrophobic colloidal silica used in the production of the magnetic toner B
One part by mass and 2.0 parts by mass of the conductive fine particles 4 were mixed with a Henschel mixer (Mitsui Miike Kakoki Co., Ltd.) to prepare a magnetic toner a. Table 3 shows the physical properties of Magnetic Toner a. <Production of Magnetic Toner b> Magnetic toner particles b having a weight average particle diameter of 6.5 μm were obtained in the same manner as in the production of the magnetic toner particles A. For 100 parts by mass of the magnetic toner particles b,
The surface was treated with 0.6 parts by mass of the hydrophobic colloidal silica used in the production of the magnetic toner A and 0.5 parts by mass of the hydrophobic titanium oxide fine powder having a BET value of 100 m ² / g after the treatment with isobutyltrimethoxysilane. Magnetic toner b was prepared by mixing with a Henschel mixer (Mitsui Miike Kakoki Co., Ltd.). Table 3 shows the physical properties of Magnetic Toner b. <Production of Magnetic Toner c> Magnetic toner particles c having a weight average particle diameter of 6.5 μm were obtained in the same manner as in the production of the magnetic toner particles A. For 100 parts by mass of the magnetic toner particles c,
0.6 parts by mass of the hydrophobic colloidal silica used in the production of the magnetic toner A and the surface were treated with isobutyltrimethoxysilane, and 0.5 part of the hydrophobic fine alumina powder having a BET value of 150 m ² / g after the treatment was mixed with a Henschel mixer. (Mitsui Miike Kakoki Co., Ltd.) to prepare magnetic toner c.
Table 3 shows the physical properties of the magnetic toner c.

The magnetic field of the obtained magnetic toner was 79.6 kA /
The magnetization intensity at m was 17.8 for the magnetic toner P, 36.5 for the magnetic toner Q, and 26 to 30 Am ² / kg for the other magnetic toners.

[0396]

[Table 3]

[0397]

Example 1 <Production of Photoconductor 1> As a photoconductor, an aluminum cylinder having a diameter of 30 mm was used as a base. Then, layers having the structure shown in FIG. 3 were sequentially laminated by dip coating to form an organic photosensitive drum 1. (1) The first layer is a conductive layer, which is mainly composed of tin oxide and titanium oxide powder dispersed in a phenol resin. The thickness is 15 μm. (2) The second layer is an undercoat layer, which is mainly composed of modified nylon and copolymerized nylon. The film thickness is 0.6 μm. (3) The third layer is a charge generating layer, which is mainly composed of an azo pigment having absorption in a long wavelength region dispersed in a butyral resin. The film thickness is 0.6 μm. (4) The fourth layer is a charge transporting layer, which is mainly composed of a hole-transporting triphenylamine compound dissolved in a polycarbonate resin (molecular weight 20,000 according to Ostwald viscosity method) at a mass ratio of 8:10, and further comprises a polytetrafluoroethylene compound. Fluorinated ethylene powder (volume average particle size 0.2 μm)
% By mass and dispersed uniformly. 25 μm thick. The contact angle of the obtained organic photosensitive drum 1 with water was 95 degrees. In addition, the measurement of the contact angle uses pure water,
Kyowa Interface Science Co., Ltd., contact angle meter CA-X type was used. <Image Forming Apparatus> As an image forming apparatus, LBP-176 is used.
0 was modified to use the same one as in FIG. 1 shown in the above embodiment. The organic photoconductor (OPC) 1 described above was used as the photoconductor 100 as an image carrier. This photoconductor 100
Then, a charging roller 117 coated with a nylon resin in which conductive carbon is dispersed as a charging member is contacted (contact pressure 6
0 g / cm), a DC voltage of -700 Vdc and an AC voltage of 2.
A bias on which 0 kVpp is superimposed is applied to uniformly charge the photosensitive member. Following charging, an electrostatic latent image is formed by exposing the image portion with a laser beam. At this time, the dark part potential Vd = -695V and the light part potential VL = -160V.

A developing sleeve 102 in which a resin layer having a layer thickness of about 7 μm and a JIS center line average roughness (Ra) of 1.0 μm having the following structure was formed on an aluminum cylinder having a blasted surface of 16 mm in diameter as a toner carrier. And a urethane rubber blade having a thickness of 1.0 mm and a free length of 1.0 mm as a toner regulating member was contacted with a developing magnetic pole of 85 mT (850 gauss) at a linear pressure of 24.5 N / m (25 g / cm). . The gap between the photoconductor 100 and the developing sleeve 102 was 290 μm.

Phenol resin: 100 parts by mass Graphite (volume average particle size: about 7 μm): 90 parts by mass Carbon black: 10 parts by mass Then, a DC voltage of -500 V and a frequency of 2000 Hz were used as a developing bias. And an AC voltage having a peak-to-peak voltage of 1650 V was used. Further, the peripheral speed of the developing sleeve is one forward direction relative to the peripheral speed of the photoconductor (94 mm / sec).
The speed was 10% (103 mm / sec).

Also, as shown in FIG. 4, the transfer roller 34 (the volume resistivity of the conductive elastic layer 34b made of ethylene-propylene rubber in which conductive carbon is dispersed is 1 × 10 ⁸ Ω · c
m, surface rubber hardness 24 degrees, diameter 20 mm, contact pressure 59 N
/ M (60 g / cm)) in FIG.
And the transfer bias was set to a DC voltage of 1.5 kV with respect to the peripheral speed (94 mm / sec).

As the fixing means, there was used a fixing device 126 which does not have an oil application function of LBP-1760 and is of a type which heats and presses with a heater via a film. At this time, a pressure roller having a surface layer of a fluororesin was used, and the diameter of the roller was 30 mm. The fixing temperature was set at 175 ° C., and the nip width was set at 7 mm.

First, toner A was used as a toner at room temperature and normal humidity (25 ° C., 60% RH), and high temperature and high humidity (30 ° C., 8%).
0% RH) and a low-temperature and low-humidity (15 ° C., 10% RH) environment. 75g for transfer material
/ M ² paper was used. As a result, high transferability was exhibited at the initial stage, and a good image without fog on non-images was obtained without any missing characters or lines during transfer.

Next, durability was evaluated using a grid image pattern composed of vertical and horizontal lines having a print area ratio of 5%.

The evaluation of abrasion of the photoconductor and fusion of the toner was made on the basis of an image defect due to abrasion or fusion of a toner, that is, a black sheet or a white spot on a halftone image in which an image defect is likely to appear. The larger the number of durable sheets before occurrence, the better the durability of the image forming method. In addition, image defects due to primary charging failure due to transfer residual toner, that is, charging unevenness were also evaluated on the halftone image. When these image defects did not occur, the durability test was continued up to 3,000 printed sheets.

In this embodiment, in the intermittent mode (that is, a mode in which the developing unit is stopped for 10 seconds each time one sheet is printed out and the deterioration of the toner is promoted by the preliminary operation at the time of restarting), 3,000 printouts are performed. The test was performed.

The image evaluation was performed as follows. (1) Image Density The image density was evaluated by maintaining the image density at the end of 3,000 prints on ordinary plain paper for copying machines (75 g / m ² ).
The image density is "Macbeth reflection densitometer RD918"
(Manufactured by Macbeth Co., Ltd.), the relative density for the printout image of the white background portion where the document density was 0.00 was measured.

A (excellent): 1.40 or more B (good): 1.35 to less than 1.40 C (good): 1.00 to less than 1.35 D (impossible): less than 1.00 (2) Image fog "REFLECMETER MODEL TC-6D
S ”(manufactured by Tokyo Denshoku Co., Ltd.) and calculating the fog density (%) from the following formula (VI) from the difference between the whiteness of the white background portion of the printout image and the whiteness of the transfer paper,
Image fog was evaluated. The smaller the value, the less fog. The filter used was a green filter.

[0408]

Fog (reflectance) (%) = reflectance on standard paper (%) − reflectance of non-image portion of sample (%) Formula (VI) A: very good (less than 1.5%) B: Good (1.5% to less than 2.5%) C: Normal (2.5% to less than 4.0%) D: Poor (4% or more) (3) Transferability The transferability is good when forming a solid black image. The transfer residual toner on the photoreceptor was taped off with a Mylar tape and stripped off, and the numerical value was obtained by subtracting the Macbeth density of the tape with only Mylar tape stuck on paper from the Macbeth density of the stripped Mylar tape stuck on paper.

A: Very good (less than 0.05) B: Good (less than 0.05 to less than 0.1) C: Normal (less than 0.1 to less than 0.2) D: Bad (more than 0.2) Initial The density was the image density of the twentieth sheet from the beginning.

[0410] The fixing offset property was 100 days from the beginning.
Observe the dirt generated on the back side of the image sample up to
The number of occurrences was counted.

[0411] The results obtained are shown in Table 4.

[0412]

[Table 4]

[0413]

Example 2 Example 1 uses toner B as the toner.
An image formation test was performed by the same image forming method as in Example 1. As shown in Table 4, very good results were obtained.

[0414]

Embodiments 3 to 17 As toners, toners C, D, E,
F, G, H, I, J, K, L, M, N, O, P or Q
And an image forming test was performed by the same image forming method as in Example 1. As a result, a practically satisfactory result was obtained as shown in Table 4.

[0415]

Examples 18 to 21 Using the toners X, Y, Z or a as the toner, an image forming test was carried out by the same image forming method as in Example 1. As a result, very good results were obtained as shown in Table 4.

[0416]

Embodiments 22 and 23 An image forming test was carried out in the same manner as in Embodiment 1, except that the toner b or c was used as the toner. As a result, good results were obtained as shown in Table 4.

[0417]

Comparative Example 1 Example 1 was conducted using toner R as the toner.
An image formation test was performed by the same image forming method as that described above. As a result, the image density was extremely low from the beginning and was not practical. Table 4 shows the results.

[0418]

Comparative Examples 2 and 3 An image forming test was performed using the toner S or T as the toner in the same image forming method as in Example 1. As a result, an image having a slightly low image density, many scatterings, and low sharpness was obtained. Table 4 shows the results.

[0419]

Comparative Example 4 Example 1 using toner U as the toner
An image formation test was performed by the same image forming method as that described above. As a result, an image having a slightly lower image density was obtained from the beginning. Table 4 shows the results.

[0420]

Comparative Example 5 Example 1 was conducted using toner V as the toner.
An image formation test was performed by the same image forming method as that described above. As a result, a charged-up image having a slightly lower image density was obtained from the beginning. Table 4 shows the results.

[0421]

Comparative Example 6 Example 1 using toner W as the toner
An image formation test was performed by the same image forming method as that described above. As a result, an image having an even lower image density than Comparative Example 5 was obtained. Table 4 shows the results.

[0422]

Embodiment 24 The toner of the present invention is also applicable to a cleanerless image forming method or an image forming method for simultaneous recovery and development.

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

First, the production of a photoreceptor as an image carrier used in the embodiments of the present invention will be described. <Manufacture of Photoconductor 2> The photoconductor is a photoconductor using an organic photoconductive material for negative charging (hereinafter referred to as an OPC photoconductor) and has a diameter of 3 mm.
A 0 mm aluminum cylinder was used as a substrate. Then, layers having the configuration shown in FIG. 8 were sequentially laminated by dip coating to form a photoreceptor 2. (1) The first layer is a conductive layer, and has a thickness of about 20 which is provided to smooth defects and the like of the aluminum cylinder and to prevent occurrence of moire due to reflection by laser exposure.
1 μm is a conductive particle-dispersed resin layer (mainly composed of tin oxide and titanium oxide powder dispersed in a phenol resin). (2) The second layer is a positive charge injection preventing layer (undercoat layer),
It serves to prevent the positive charge injected from the aluminum support from canceling out the negative charge charged on the surface of the photoreceptor, and 1 × 10 ⁶ Ω ·
This is a medium resistance layer having a thickness of about 1 μm and a resistance adjusted to about cm. (3) The third layer is a charge generation layer, which is a layer having a thickness of about 0.3 μm in which a disazo pigment is dispersed in butyral resin, and generates a positive and negative charge pair by receiving laser exposure. (4) The fourth layer is a charge transport layer, a layer having a thickness of about 25 μm in which a hydrazone compound is dispersed in a polycarbonate resin, and is a P-type semiconductor. Therefore, the negative charges charged on the photoreceptor surface cannot move through this layer, and only the positive charges generated in the charge generation layer can be transported to the photoreceptor surface. (5) The fifth layer is a charge injection layer, which comprises a photocurable acrylic resin, conductive tin oxide ultrafine particles, and a volume average particle size of about 0.1 μm.
It is a dispersion of 25 μm tetrafluoroethylene resin particles. Specifically, tin oxide particles having a volume average particle diameter of about 0.03 μm, which is doped with antimony and reduced in resistance, are 100% by mass with respect to the resin, 20% by mass of ethylene tetrafluoride resin particles, and 1% of a dispersant. .2% by mass. The coating liquid thus prepared was applied to a thickness of about 2.5 μm by a spray coating method, and was cured by light irradiation to form a charge injection layer.

The volume resistivity of the surface of the obtained photosensitive member 2 is
The contact angle of the photoreceptor surface with water was 5 × 10 ¹² Ω · cm, and was 102 degrees.

Next, an example of manufacturing the charging member used in the embodiment of the present invention will be described. <Production of Charging Member 1> S having a diameter of 6 mm and a length of 264 mm
US roller as a core, urethane resin, carbon black as conductive particles on the core, a medium-resistance urethane foam layer formulated with a sulfide agent, a foaming agent, etc. is formed into a roller shape, and further cut and polished to form The surface properties were adjusted, and a charging roller having a diameter of 12 mm and a length of 234 mm was prepared as a flexible member.

The obtained charging roller has a volume resistance of 1 ×.
10 ⁵ Ω · cm and hardness is 30 as Asker C hardness.
Degree. When the surface of the charging roller was observed with a scanning electron microscope, the average cell diameter was about 100 μm.
The porosity was 60%.

FIG. 5 is a schematic structural diagram of an example of the image forming apparatus according to the present invention.

The image forming apparatus used in the twenty-fourth embodiment is a laser printer (recording apparatus) of a cleaning simultaneous development process (cleanerless system) using a transfer type electrophotographic process. It has a process cartridge from which a cleaning unit having a cleaning member such as a cleaning blade is removed, uses a magnetic one-component toner as a toner, and is arranged so that a toner layer on a toner carrier and an image carrier are not in contact with each other. This is an example of non-contact development. (1) Overall Schematic Configuration of Image Forming Apparatus of the Present Example A rotating drum type OPC photoconductor 21 using the photoconductor 2 as an image carrier is 94 mm / sec in the X direction of the arrow.
Is driven to rotate at a peripheral speed (process speed).

The charging roller 22, which is the charging member 1 as a contact charging member, is disposed in pressure contact with the photoreceptor 21 with a predetermined pressing force against elasticity. n is photoconductor 2
1 is a charging contact portion that is a contact portion between the charging roller 22.
In the present example, the charging roller 22 has a charging contact portion n which is a contact surface with the photoconductor 21 and has a charging contact portion n in a facing direction (direction of arrow Y).
It is driven to rotate at a peripheral speed of 0%. That is, the surface of the charging roller 22 as a contact charging member has a speed difference from the surface of the photoconductor 21. That is, the surface of the charging roller 22 as a contact charging member has a relative speed difference of 200% relative to the surface of the photoconductor 21. Further, the amount of application is approximately 1 × 10 ⁴ /
The conductive fine particles 3 were applied so as to be uniform in mm ² .

Further, a DC voltage of -700 V was applied as a charging bias from a charging bias applying power source to the core metal 22a of the charging roller 22. In this example, the photoconductor 21
Is uniformly charged by the direct injection charging method to a potential (-680 V) substantially equal to the voltage applied to the charging roller 22. This will be described later.

A laser beam scanner (exposure device) 23 including a laser diode, a polygon mirror and the like as exposure means.
Outputs a laser beam whose intensity is modulated in accordance with a time-series electric digital pixel signal of target image information, and scans and exposes the uniformly charged surface of the photoconductor 1 with the laser beam. By this scanning exposure, an electrostatic latent image corresponding to the target image information is formed on the surface of the rotating photoconductor 21. Developing device 2 as developing means
Due to 4, the electrostatic latent image on the surface of the photoconductor 21 is developed as a toner image.

The developing device 24 of this embodiment is a non-contact type reversal developing device using a negatively chargeable magnetic one-component insulating toner X as a toner. The conductive fine particles 1 are externally added to the toner X.

As a toner carrier, a developing sleeve 24a in which a resin layer having a layer thickness of about 7 μm and a JIS center line average roughness (Ra) of 1.0 μm having the following structure is formed on a 16 mm diameter aluminum cylinder whose surface is blasted. And a magnet roll having a developing magnetic pole of 90 mT (900 gauss) and a urethane elastic blade 24c having a thickness of 1.0 mm and a free length of 1.5 mm as a toner regulating member.
The contact was performed at a linear pressure of 4 N / m (30 g / cm). The gap between the photoconductor 21 and the developing sleeve 24a was 290 μm.

Phenol resin: 100 parts by mass Graphite (volume average particle size: about 7 μm): 90 parts by mass Carbon black: 10 parts by mass Further, the developing sleeve 24 a is opposed to the photoconductor 21. 120% of the peripheral speed of the photosensitive member 21 in the forward direction (the direction of the arrow W) with respect to the rotation direction of the photosensitive member 21
At a peripheral speed of.

The elastic blade 2 is attached to the developing sleeve 24a.
At 4c, the toner is coated in a thin layer. The layer thickness of the toner with respect to the developing sleeve 24a is regulated by the elastic blade 24c, and the toner is charged. At this time, the developing sleeve 24
The amount of the toner coated on a was 15 g / m ² .

[0437] The toner coated on the developing sleeve 24a is conveyed to the developing section a, which is the opposing portion of the photosensitive member 21 and the developing sleeve 24a, by the rotation of the developing sleeve 24a. A developing bias voltage is applied to the sleeve 24a from a developing bias applying power source. A developing bias voltage is obtained by superimposing a DC voltage of −420 V and a rectangular AC voltage having a frequency of 1600 Hz and a peak-to-peak voltage of 1500 V (electric field intensity of 5 × 10 ⁶ V / m).
One-component jumping development was performed between a and the photosensitive member 21a.

The transfer roller 25 of medium resistance as a contact transfer means is brought into pressure contact with the photosensitive member at a linear pressure of 98 N / m (100 g / cm) to form a transfer nip b. A transfer material P as a recording medium is supplied to the transfer nip b from a paper supply unit (not shown) at a predetermined timing.
5, a predetermined transfer bias voltage is applied from a transfer bias application power source, so that the toner image on the photoconductor 21 side is sequentially transferred to the surface of the transfer material P fed to the transfer nip portion b.

In this example, the volume resistance of the transfer roller 25 is 5
The transfer was performed by applying a DC voltage of +2900 V using a material of × 10 ⁸ Ω · cm. That is, the transfer material P introduced into the transfer nip portion b is conveyed by nipping the transfer nip portion b, and the toner image formed and carried on the surface of the photoreceptor 21 on its surface side is sequentially subjected to electrostatic force and pressing force. Is transcribed. The transfer material P fed to the transfer nip portion b and having received the transfer of the toner image on the photoconductor 21 side is separated from the surface of the photoconductor, and is introduced into a fixing unit 26 such as a heat fixing method as a fixing unit. After the toner image is fixed, it is discharged out of the apparatus as an image formed product (print, copy).

In the image forming apparatus of this embodiment, the cleaning unit is removed, and the transfer residual toner remaining on the surface of the photoreceptor 21 after the transfer of the toner image to the transfer material P is not removed by the cleaner. With the rotation of, the cleaning unit 24 reaches the developing unit a via the charging contact unit n, and is cleaned (collected) at the same time as the development in the developing unit 24.

Reference numeral 27 denotes an image forming apparatus and a process cartridge which are detachable from the image forming apparatus main body. The image forming apparatus according to the present embodiment is configured as an image forming apparatus and a process cartridge which are detachable from a printer main body by integrally integrating three process devices of a photoconductor 21, a charging roller 22, and a developing device 26. The combination of the image forming apparatus and the process device to be formed into a process cartridge is not limited to the above, and is arbitrary. Reference numeral 28 denotes a process cartridge attachment / detachment / holding member. (2) Behavior of conductive fine particles in this embodiment The conductive fine particles mixed into the toner of the developing device 24 are exposed to an appropriate amount together with the toner when the developing device 24 develops the toner of the electrostatic latent image on the photoconductor 21 side. Move to the body 21 side.

The toner image on the photoreceptor 21 is attracted to the transfer material P, which is a recording medium, by the influence of the transfer bias in the transfer portion b and is positively transferred. Due to the conductivity, the toner is not positively transferred to the transfer material P side, but remains substantially adhered and held on the photoconductor 21.

In the present invention, since the image forming apparatus has no cleaning step, the transfer residual toner remaining on the surface of the photoreceptor 1 after the transfer and the residual conductive fine particles are
The photoconductor 21 and the charging contact portion n of the charging roller 22 serving as a contact charging member are carried as it is by the movement of the surface of the photoconductor 21, and adhere to or mix with the charging roller 22. Therefore, direct injection charging of the photoconductor 21 is performed in a state where the conductive fine particles are present at the charging contact portion n between the photoconductor 21 and the charging roller 22.

The presence of the conductive fine particles enables the charging roller 22 to maintain close contact and contact resistance with the photosensitive member 21 even when toner adheres to or mixes with the charging roller 22. The direct injection charging of the photoconductor 21 can be performed.

That is, the charging roller 22 comes into close contact with the photosensitive member 21 via the conductive fine particles, and the conductive fine particles existing on the mutual contact surface between the charging roller 22 and the photosensitive member 21 are removed.
By rubbing the surface without gaps, the charging of the photoreceptor 21 by the charging roller 22 is dominated by stable and safe direct injection charging without using a discharge phenomenon due to the presence of conductive fine particles. A high charging efficiency that could not be obtained is obtained, and a potential substantially equal to the voltage applied to the charging roller 22 can be given to the photoconductor 21.

The transfer residual toner adhering or mixed into the charging roller 22 is gradually discharged from the charging roller 22 onto the photosensitive member 21 and moves to the developing section a with the movement of the surface of the photosensitive member 21. Collection)
Is done.

In the simultaneous cleaning for development, the toner remaining on the photoreceptor 21 after transfer is developed during the subsequent image forming process, that is, the photoreceptor is charged and exposed to form a latent image, and the latent image is developed. At the time, the toner is collected by a fog removing bias of the developing device, that is, a fog removing potential difference Vback which is a potential difference between a DC voltage applied to the developing device and a surface potential of the photoconductor. In the case of the reversal development as in the image forming apparatus in this embodiment, the simultaneous cleaning for development is performed by the electric field for collecting the toner from the dark portion potential of the photosensitive member to the developing sleeve by the developing bias, and the light portion potential of the photosensitive member from the developing sleeve. This is done by the action of an electric field that causes toner to adhere to the surface.

When the image forming apparatus is operated,
The conductive fine particles mixed into the toner of the developing device 24 move to the surface of the photoreceptor 21 in the developing unit a and are carried to the charging contact unit n via the transfer unit b by the movement of the image bearing surface, so that the charging contact unit n is charged. Because new conductive fine particles are continuously supplied to the part n,
Even if the conductive fine particles are reduced due to dropping or the like in the charging contact portion n or the conductive fine particles are deteriorated, a decrease in the chargeability is prevented from occurring, and the good chargeability is stably maintained. Will be maintained.

Thus, in the image forming apparatus of the contact charging system, the transfer system, and the toner recycling process, the simple charging roller 22 is used as the contact charging member, and the charging roller 22 is not affected by the transfer residual toner. Ozone-less direct injection charging can be stably maintained over a long period of time with an applied voltage, uniform charging properties can be provided, and there is no obstacle due to ozone products, poor charging, etc., simple configuration, low cost It is possible to obtain a simple image forming apparatus.

As described above, the conductive fine particles have an electric resistance of 1 × 10 ⁹ Ω · cm in order not to impair the chargeability.
Must be: When a contact developing device in which the toner directly contacts the photoconductor 21 in the developing unit a is used,
Charge may be injected into the photoconductor 21 by the developing bias through the conductive fine particles in the toner, and image fog may occur.

However, in this embodiment, since the developing device is a non-contact type developing device, a good image can be obtained without a developing bias being injected into the photosensitive member 21. Also,
Since no charge is injected into the photoconductor 21 in the developing section a, the developing sleeve 24a and the photoconductor 2
It is possible to provide a high potential difference between the conductive particles, and the conductive fine particles are easily developed uniformly. Property can be obtained, and a good image can be obtained.

A contact surface n between the charging roller 22 and the photosensitive member 21
With the conductive fine particles interposed therebetween, it is possible to easily and effectively provide a speed difference between the charging roller 22 and the photoconductor 21 due to the lubricating effect (friction reducing effect) of the conductive fine particles.

By providing a speed difference between the charging roller 22 and the photosensitive member 21, the chance of contact of the conductive fine particles with the photosensitive member 21 at the mutual contact surface n between the charging roller 22 and the photosensitive member 21 is greatly increased. , High contact properties, and good direct injection charging.

In this embodiment, the charging roller 22 is driven to rotate, and the rotating direction is rotated in a direction opposite to the moving direction of the surface of the photosensitive member 21. An effect of temporarily collecting the transfer residual toner on the charging roller 21 to the charging roller 22 and leveling the toner is obtained. That is, it is possible to perform direct injection charging by dominating the transfer residual toner on the photoreceptor 21 once by reverse rotation and performing charging.

Further, in this embodiment, the lubricating effect of the photosensitive member 21 as the image carrier and the charging roller 22 as the contact charging member is provided by an appropriate amount of conductive fine particles in the charging contact portion n. The friction between the charging roller 22 and the photoconductor 21 is reduced by the
It is easy to rotate and drive with a speed difference. That is, the driving torque is reduced, and the charging roller 22 and the photosensitive member 2
The surface 1 can be prevented from being scraped or scratched. Further, sufficient charging performance can be obtained by increasing the chance of contact by the conductive fine particles. Further, there is no adverse effect on image formation due to the conductive fine particles falling off from the charging roller 22. (3) Evaluation In this example, 200 g of the toner X was filled in the toner cartridge, and the toner cartridge was used until the toner amount became small in the toner cartridge by intermittent printing of 3000 sheets with 3% coverage. 75 g / m ² of A for transfer material
3000 sheets were printed intermittently using 4 copy papers, but no decrease in developability was observed.

After 3000 sheets of intermittent printing, the portion corresponding to the contact portion n with the photoreceptor 21 was taped on the charging roller 22 and observed. It is covered with white zinc oxide particles (conductive fine particles 1), and the intervening amount is about 3 × 10 ⁵
Pieces / mm ² . When the transfer residual toner interposed in the contact portion between the charging member and the image carrier was observed with a scanning microscope, it was found that the surface was covered as if it was fixed with conductive fine particles having a very small particle diameter. No transfer residual toner was observed.

Since the conductive fine particles 1 are present at the contact portion n between the photoreceptor 21 and the charging roller 22 and the resistance of the conductive fine powder is sufficiently low at 1500 Ω · cm, 3,000 sheets from the initial stage. No image defects due to charging failure occurred after the intermittent printing, and good direct injection charging properties were obtained.

Further, since the photosensitive member 2 having a volume resistance of the outermost surface layer of 5 × 10 ¹² Ω · cm is used as an image carrier, a character image having a sharp outline can be maintained by maintaining an electrostatic latent image. Is obtained, and it is possible to realize direct injection charging in which sufficient chargeability is obtained even after 3000 sheets of intermittent printing. 3000
The photoconductor potential after direct injection charging after intermittent printing of a sheet is -675 V with respect to the applied charging bias of -700 V,
The decrease in chargeability from the beginning was as small as 25 V, and no deterioration in image quality due to the decrease in chargeability was observed.

Further, in combination with the use of the photosensitive member 2 having a contact angle of 102 degrees with water on the surface of the image carrier,
The transfer efficiency was excellent at the initial stage and after 3000 intermittent printing. Considering that the amount of untransferred toner on the photoreceptor after transfer is small, the amount of untransferred toner on the charging roller 2 after the intermittent printing of 3000 sheets is small, and there is little fog in the non-image area. This indicates that the recoverability of the transfer residual toner in the development was good. In addition, 300
Even after the zero intermittent printing, the scratch on the photoreceptor was slight, and the image defect generated on the image corresponding to the scratch was suppressed to a practically acceptable level.

Among the methods for evaluating printed images, (1) image density, (2) image fog, and (3) transferability were the same as in Example 1. (4) Charging Property The photoreceptor surface potential after uniform charging was measured by arranging a sensor at the developing device position after the completion of the printout test, and the charging property was evaluated based on the difference. The larger the difference is, the larger the decrease in chargeability is. (5) Amount of conductive fine particles in the contact portion between the image bearing member and the contact charging member The amount of the conductive fine particles in the contact portion between the photosensitive member and the contact charging member was measured by the method described above. 1 × 10 ^{4 to} 5 × 1
0 interposition of ⁵ / mm ² is preferred. (6) Photoreceptor Scratches After the printout test was completed, the occurrence of scratches on the photoreceptor drum surface and the adhesion of toner to the scratches and the effect on the printout image were visually evaluated.

A: very good (not generated) B: good (slight flaws are seen, but there is no effect on the image) C: normal (there is toner sticking or flaws, but no effect on the image) D: poor (many toner adheres along the scratch, causing vertical streak-like image defects)

[0462]

Examples 25 to 27 An image forming test was conducted in the same manner as in Example 24 except that toners Y, Z or a shown in Table 3 were used instead of the toner X used in Example 24. Table 5 shows the results.

[0463]

Example 28 Image characteristics and durability were evaluated under the same conditions as in Example 24, except that the charging member 2 was a charging member manufactured as follows. FIG. 6 is a schematic diagram of the image forming apparatus used in this embodiment. That is, the charging means is a charging brush 22 'using the charging member B. Table 5 shows the obtained results. <Manufacture of charging member 2> SU of φ6 mm and length of 264 mm
An S roller was used as a core metal, and a tape in which conductive nylon fibers were piled on the core metal was spirally wound around a metal core metal to prepare a roll-shaped charging brush. The fiber thickness is 6 denier (300 denier / 50 filament), the resistance of which is adjusted by dispersing carbon black in nylon fiber, the brush fiber length is 3 mm, and the brush density is 100,000 per square inch. The used material was used. The volume resistance value of the obtained charging brush roll is 1 × 10 ⁷ Ω · c.
m.

[0464]

[Table 5]

[0465]

According to the present invention, the particle size distribution of the magnetic material contained is precisely controlled, the ratio of the iron element content / carbon element content on the surface is less than 0.001, and the average circularity The use of a special magnetic toner with an average particle size of 0.970 or more provides excellent environmental stability, does not cause abrasion of the photoconductor or toner fusion, and provides a high-quality image with high resolution even at low humidity. Obtained for a stable period.

According to the present invention, in an image forming method comprising a contact charging method and a magnetic one-component developing method, the ratio of iron element content / carbon element content on the surface is less than 0.001, and the average circularity is less than 0.001. By using a special toner of 0.970 or more, abrasion of the photoreceptor and fusion of the toner do not occur, and a high-quality and high-resolution image can be stably obtained for a long time even under low humidity.

Further, the use of a special toner having inorganic fine particles and conductive fine particles on the surface, the magnetic substance being substantially not exposed on the surface, and having an average circularity of 0.970 or more, provides high quality. Thus, an image having high resolution and excellent fog and transferability can be obtained.

Further, in the image forming method comprising the contact charging method and the magnetic one-component developing method using the toner of the present invention, and in the image forming apparatus of the contact charging method, the contact transfer method, and the toner recycling process, the contact charging member is used. Overcomes the inhibition of charging due to the adhesion and mixing of the toner onto the transfer residual toner, makes the charging of the image carrier good, and is good even when used repeatedly over a long period of time or when the toner cartridge is used until the toner amount is reduced. A stable image can be obtained.

Further, by using a simple member as the contact charging member, it is possible to stably maintain ozone-less direct injection charging at a low applied voltage for a long period of time irrespective of contamination of the contact charging member by transfer residual toner, It is possible to provide a simple configuration, low cost image forming apparatus and a process cartridge which can provide uniform chargeability and are free from troubles due to ozone products and troubles due to poor charging.

Further, over a long period of repeated use, scratches on the image carrier caused by interposing conductive fine particles in the contact portion between the charging member and the image carrier can be greatly reduced, and image defects on the image can be suppressed. can do.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus for performing a method of the present invention.

FIG. 2 shows a schematic configuration diagram of a developing device for one-component development for performing the method of the present invention.

FIG. 3 is a schematic structural view of an image carrier for carrying out the method of the present invention.

FIG. 4 is a schematic structural view of a contact transfer member for performing the method of the present invention.

FIG. 5 is a schematic configuration diagram of an image forming apparatus according to Examples 24 to 27.

FIG. 6 is a schematic configuration diagram of an image forming apparatus according to a twenty-eighth embodiment.

FIG. 7 shows a charging characteristic graph of a contact charging member.

FIG. 8 is a schematic diagram showing a layer structure of an image carrier for carrying out the method of the present invention.

[Explanation of symbols]

 100: photoreceptor 102: developing sleeve 114: transfer roller 116: cleaner 117: charging roller 121: laser beam scanner 124: register roller 125: transport belt 126: fixing device 140: developing device 141: stirring member P: transfer material 103: Elastic blade 104: Magnet roller 34: Transfer roller 34a: Core bar 34b: Elastic layer 21: Photoconductor 22: Charging roller 22 ': Charging brush 22a: Core bar 23: Laser beam scanner 24: Developing device 24a: Developing sleeve 24b: Stirring member 24c: elastic blade (layer regulating member) 25: transfer roller 26: fixing device 26a: heater 26b: fixing film 26c: pressure roller 27: process cartridge 28: cartridge holding member 11: aluminum base 12: conductive layer 13: Injection prevention layer 14 The charge generation layer 15: charge transport layer 16: charge injection layer 16a: conductive particles (conductive filler)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 9/08 375 G03G 15/02 101 9/087 102 15/02 101 15/06 101 102 15/08 501D 15/06 101 504 15/08 501 9/08 101 504 302 384 (72) Inventor Tatehiko Chiba 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Tsuyoshi Takiguchi Ota-ku, Tokyo 3-30-2 Shimomaruko Canon Inc. (72) Inventor Akira Hashimoto 3-30-2 Shimomaruko 3-chome, Ota-ku, Tokyo Inside Canon Inc. (72) Motoki Hisaki 3-chome Shimomaruko, Ota-ku, Tokyo No. 30 No. 2 F term in Canon Inc. (reference) 2H003 BB11 CC05 CC06 DD03 2H005 AA02 AA03 AA06 AA08 AA15 AB06 CA12 CA14 CA26 CB03 CB07 CB13 EA01 EA02 EA03 EA05 EA07 EA10 2H073 AA03 BA03 BA13 BA45 CA02 2H077 AA37 AD02 AD06 AD13 AD17 AD23 AD31 AD36 BA07 EA13 FA01 FA21 GA01

Claims (50)

[Claims] 1. A magnetic toner having inorganic fine particles on the surface of magnetic toner particles containing at least a binder resin, a wax and a magnetic material, wherein the average circularity of the magnetic toner is 0.970 or more; Contains at least a magnetic iron oxide as the magnetic substance, and the amount of the iron element relative to the amount of the carbon element present on the surface of the magnetic toner particles (A) measured by X-ray photoelectron spectroscopy of the magnetic toner Ratio of (B) (B / A)
Is less than 0.001, and the magnetic strength of the magnetic toner in a magnetic field of 79.6 kA / m (1000 Oe) is 10 to 50 Am ² / k.
g (emu / g), the wax has a maximum endothermic peak in a differential scanning calorimetry (DSC) curve of 40 to 120 ° C., and the volume average particle diameter of the magnetic substance is 0.1 to 0.3 μm. And
A magnetic toner, wherein the number% of particles having a particle size of 0.03 to 0.1 μm is 40% or less. 2. The magnetic material has a true density of 4.5 to 5.5 g.
/ Cm ³ and a bulk density of 0.37 to 1.00 g / cm ³
The magnetic toner according to claim 1, wherein 3. The method according to claim 1, wherein the particles of the magnetic material are 0.03 to 0.1.
The magnetic toner according to claim 1, wherein the number% of particles having a particle size of 1 μm is 1% to 30%, and the number% of particles having a particle size of 0.3 μm or more is 10% or less. 4. The magnetic toner according to claim 1, wherein the number% of particles of 0.3 μm or more in the magnetic material is 5% or less. 5. The bulk density of the magnetic material is 0.40 to 0.8.
A magnetic toner according to any one of claims 1 to 4, characterized in that a 0 g / cm ^3. 6. The magnetic toner according to claim 1, wherein the magnetic material has been surface-treated with a coupling agent in an aqueous medium. 7. The projection area circle equivalent diameter of the magnetic toner is C
And a toner particle satisfying the relationship of D / C ≦ 0.02, where D is the minimum value of the distance between the surface of the magnetic particle and the surface of the toner particle in the cross-sectional observation of the magnetic toner using a transmission electron microscope (TEM). The magnetic toner according to any one of claims 1 to 6, wherein the ratio is 50% by number or more. 8. The magnetic toner according to claim 7, wherein the ratio of the magnetic toner particles satisfying the relationship of D / C ≦ 0.02 is 65% by number or more. 9. The magnetic toner according to claim 7, wherein the ratio of the magnetic toner particles satisfying the relationship of D / C ≦ 0.02 is 75% by number or more. 10. The mode circularity of the magnetic toner is:
The magnetic toner according to claim 1, wherein the ratio is 0.990 or more. 11. The magnetic toner according to claim 1, wherein the magnetic toner particles are obtained by a polymerization method. 12. The magnetic toner according to claim 1, wherein the polymerization method is a suspension polymerization method. 13. The magnetic toner according to claim 1, wherein the magnetic toner contains a wax in an amount of 0.1 to 20% by mass based on the whole magnetic toner. 14. The differential scanning calorimetry (D) of the wax.
SC) The maximum endothermic peak in the curve is 40-110 ° C.
The magnetic toner according to claim 1, wherein: 15. The wax differential scanning calorimetry (DS)
The magnetic toner according to any one of claims 1 to 13, wherein the maximum endothermic peak in the curve (C) is 45 to 90 ° C. 16. The magnetic toner according to claim 1, wherein the inorganic fine particles have a number-average primary particle diameter of 4 to 80 nm, and are hydrophobic inorganic particles. . 17. The method according to claim 1, wherein the inorganic fine particles have a number average primary particle size of 4 to 80 nm, and are at least one kind of inorganic fine particles selected from silica, titanium oxide and alumina, or a composite oxide thereof. 17. The magnetic toner according to any one of claims 16 to 16. 18. The method according to claim 1, wherein the inorganic fine particles are treated with at least silicone oil.
18. The magnetic toner according to any one of claims 17 to 17. 19. The magnetic toner according to claim 1, wherein the inorganic fine particles are treated with at least a silane compound and silicone oil. 20. The magnetic toner according to claim 1, wherein the magnetic toner contains conductive fine particles having a volume average particle diameter smaller than the weight average particle diameter of the magnetic toner. Magnetic toner. 21. The resistance of the conductive fine particles is 1 × 10
21. The magnetic toner according to claim 20, which has a resistivity of ^9? Cm or less. 22. The resistance of the conductive fine particles is 1 × 10
The magnetic toner according to claim 20, wherein the magnetic toner has a resistivity of ⁶ Ω · cm or less. 23. The magnetic toner according to claim 20, wherein the conductive fine particles are non-magnetic. 24. A charging step of applying a voltage to the charging member to charge the image carrier, an electrostatic latent image forming step of forming an electrostatic latent image on the charged image carrier, and A developing step of transferring the toner carried on the toner carrier to the formed electrostatic latent image to form a toner image on the image carrier; and transferring the toner image formed on the image carrier to a transfer material. An image forming method comprising: a transfer step of performing electrostatic transfer, wherein an image is repeatedly formed on an image carrier. In the developing step, the toner on the toner carrier is any one of claims 1 to 23. The charging step, wherein the charging step is a step of charging the image carrier by applying a voltage to a charging member that contacts the image carrier by forming a contact portion. Image forming method. 25. The method according to claim 2, wherein the developing step also serves as a cleaning step of collecting the toner remaining on the image carrier after transferring the toner image onto the transfer material.
5. The image forming method according to item 4. 26. In the charging step, conductive fine particles contained in the magnetic toner adhere to the image carrier in the developing step and remain on the image carrier after the transfer step, and at least the charging member and the image bearing member The image forming method according to claim 24 or 25, wherein the image forming method is carried to and / or interposed in a contact portion of a body and / or in the vicinity thereof. 27. The charging step, wherein the contact portion between the charging member and the image carrier is 1 × 10 ^{3 to} 5 × 10 ⁵ / mm ^2.
27. The image forming method according to claim 24, wherein the image carrier is charged with the conductive fine particles interposed therebetween. 28. The charging step, wherein the moving speed of the surface of the charging member forming the contact portion and the moving speed of the surface of the image carrier have a relative speed difference, and the image carrier is charged. The image forming method according to any one of claims 24 to 27, wherein: 29. The charging method according to claim 24, wherein the charging step is a step of charging the image carrier while the charging member and the image carrier move in directions opposite to each other. 2. The image forming method according to 1., 30. The charging step, wherein the image carrier is charged by applying a voltage to a roller member having a Asker C hardness of 50 degrees or less as the charging member. Item 30. The image forming method according to any one of Items 24 to 29. 31. The charging step is a step of charging an image carrier by applying a voltage to the roller member, wherein the roller member has at least a surface having an average cell diameter of 5 to 300 μm in spherical conversion. Has a certain depression,
The porosity of the surface of the roller member having the recess as a void portion is 1
31. The image forming method according to claim 24, wherein the ratio is 5 to 90%. 32. The method according to claim 24, wherein the charging step is a step of charging the image carrier by applying a voltage to a conductive brush member as the charging member. The image forming method according to claim 1. 33. The charging step according to claim 31, wherein the volume resistivity is 1 × 10
The image forming method according to any one of claims 24 to 32, characterized in that by applying a voltage to the charging member ^{3 ~1} × 10 ^{8 Ω} · cm is a step of charging the image bearing member. 34. The charging step includes applying a DC voltage or a voltage obtained by superimposing a DC voltage or an AC voltage having a peak voltage less than 2 × Vth (Vth: discharge start voltage in applying a DC voltage) (V) to the charging member. 3. The step of charging the image carrier by applying the voltage.
The image forming method according to any one of Items 4 to 33. 35. The charging step is a step of charging the image carrier by applying to the charging member a DC voltage or a voltage obtained by superimposing an AC voltage having a peak voltage less than Vth (V) on a DC voltage. The image forming method according to any one of claims 24 to 33, wherein: 36. The apparatus according to claim ^24, wherein the outermost layer of the image carrier has a volume resistivity of 1 × 10 ⁹ to 1 × 10 ¹⁴ Ω · cm. Image forming method. 37. The image forming apparatus according to claim 24, wherein the outermost surface layer of the image carrier is a resin layer in which conductive fine particles made of at least a metal oxide are dispersed. Image forming method. 38. The outermost surface layer of the image carrier is a resin layer in which at least one or more lubricating fine particles selected from fluorine resin particles, silicone resin particles, and polyolefin resin particles are dispersed. Claim 2
The image forming method according to any one of Items 4 to 37. 39. A contact angle of the image carrier with water is as follows:
The image forming method according to any one of claims 24 to 38, wherein the angle is 85 degrees or more. 40. The image forming method according to claim 24, wherein the image carrier is a photoconductor using a photoconductive substance. 41. The image forming method according to claim 24, wherein in the electrostatic latent image forming step, an electrostatic latent image is formed on an image carrier by image exposure. 42. In the developing step, the moving speed of the toner carrier surface in the developing area is 0.7 to 3.0 times the moving speed of the image carrier surface. The image forming method according to any one of the above. 43. The image forming apparatus according to claim 24, wherein, in the developing step, the surface roughness (Ra) of the toner carrier is 0.2 to 3.5 μm. Method. 44. The developing step comprises:
44. A developing step of forming a toner layer of about 50 g / m < ² > and transferring the toner from the toner layer to an image carrier to form a toner image. Image forming method. 45. The method according to claim 24, wherein in the developing step, an amount of the toner carried on the toner carrier is regulated by a toner layer thickness regulating member abutting on the toner carrier. An image forming method according to any one of the preceding claims. 46. The image forming method according to claim 45, wherein the toner layer thickness regulating member is an elastic member. 47. In the developing step, a magnetic toner layer is formed on the toner carrier with a thickness smaller than a gap between the image carrier and the toner carrier, and the toner is transferred from the toner layer to an electrostatic latent image. 47. The image forming method according to claim 24, further comprising a developing step of forming a toner image on the image carrier by causing the toner image to be formed. 48. The image forming apparatus according to claim 24, wherein in the developing step, the image bearing member and the toner bearing member are arranged so as to face each other with a predetermined gap therebetween, and the gap is 100 to 1000 μm. 48. The image forming method according to any one of items 47 to 47. 49. The developing step is a step of developing an electrostatic latent image on the image carrier by applying at least an AC electric field as a developing bias between the toner carrier and the image carrier. 3 × 10 with peak-to-peak electric field strength
The image forming method according to any one of claims 24 to 48, wherein the frequency is ⁶ to 10 x 10 ⁶ V / m and the frequency is 100 to 5000 Hz. 50. The transfer step, wherein the transfer member is in contact with the image carrier via the transfer material at the time of transfer, and the toner image on the image carrier is transferred to the transfer material. The image forming method according to any one of claims 24 to 49.