JP2001343783A - Magnetic toner and method for forming image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic toner which can maintain satisfactory performance of the toner, even if the toner is left in a severe environment and which can stably form images of high definition over a long time, even if the toner is used, left standing in the severe environment. SOLUTION: In the magnetic toner, having inorganic fine particles deposited on the surfaces of magnetic toner particles containing at least a binder resin, a release agent and a magnetic material, the magnetic toner has >=0.970 average circularity and 3 to 10 μm weight average particle size (D4). The magnetic toner particles contain magnetic iron oxide as the magnetic material. The magnetic toner has 10 to 50 Am2/kg (emu/g) magnetization in 79.6 kA/m (1,000 Oe) of magnetic field. The magnetic material has properties such that if the absorbance is a-5 of the material in a dispersed state in hexane solution at 500 nm, five minutes after dispersion, and if the absorbance is a-30 at 500 nm 30 minutes after dispersion, the inequality 0.8<a-30/a-5 is satisfied. The magnetic toner is used for the method for image formation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner for visualizing an electrostatic latent image using an electrophotographic method, an electrostatic recording method, a magnetic recording method, a toner jet recording method, and the like, and an image forming method. It is about.

[0002]

2. Description of the Related Art Conventionally, many methods have been known as electrophotography. In general, a photoconductive substance is used to form an image on an image carrier (hereinafter, also referred to as a "photoconductor") by various means. An electric latent image is formed on the transfer material, and then the latent image is developed with toner to form a visible image, and if necessary, the toner image is transferred to a transfer material such as paper. To obtain a copy by fixing the toner image to the toner image.

[0003] Methods of visualizing an electric latent image with toner include a cascade developing method, a magnetic brush developing method, a pressure developing method, a magnetic brush developing method using a two-component toner composed of a carrier and a toner, and a toner carrier. A non-contact one-component developing method in which toner is caused to fly from the toner carrier to the image carrier in non-contact with the image carrier, a contact one-component developing method in which the toner carrier is pressed against the image carrier and the toner is transferred by an electric field,
Further, a so-called jumping method is also used in which a magnetic sleeve is used, and a rotating sleeve having a magnetic pole disposed in the center is used to fly between the photosensitive member and the sleeve by an electric field.

As a jumping method, for example, in Japanese Patent Application Laid-Open No. 54-43027, an insulating magnetic developer is thinly applied on a toner carrier, triboelectrically charged, and then subjected to a magnetic field. A method is disclosed in which an electrostatic latent image is brought very close to, opposed to, without contact, and developed. According to this method, by applying an insulating magnetic developer thinly on the toner carrier, sufficient frictional charging of the developer is enabled, and the developer is supported by a magnetic force without contacting the electrostatic latent image. Since the development is performed, transfer of the developer to the non-image area, that is, fogging is suppressed, and a high-definition image can be obtained.

[0005] 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.

[0006] In recent years, LED and LBP printers have become the mainstream in the printer market, and the direction of technology has been changed 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 copiers are also becoming more sophisticated, and for this reason, they are moving toward digitalization. In this direction, the method of forming an electrostatic latent image with a laser is the main method, so it is also proceeding in the direction of high resolution, and here, similarly to the printer, a high-resolution and high-definition developing method is required. I have. As one means for satisfying this requirement, the particle size of toner has been reduced.
No. 3, JP-A-1-191156, JP-A-2-191
214156, JP-A-2-284158,
JP-A-3-181952, JP-A-4-16204
In Japanese Patent Application Publication No. 8 and the like, a toner having a specific particle size distribution and a small particle size is proposed.

On the other hand, the toner image formed on the photoreceptor in the developing step is transferred to a transfer material in the transfer step, but the untransferred toner in the image area and the fog toner in the non-image area remaining on the photoreceptor are cleaned. It is cleaned in the process and stored in a waste toner container. For this cleaning process, conventional blade cleaning, fur brush cleaning,
Roller cleaning or the like is used. 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 aiming for a more compact apparatus. Further, from the viewpoint of ecology, a system with a small amount of waste toner is desired in terms of effective use of the toner, and a toner with high transfer efficiency and low fog has been demanded.

The developer used in such an image forming process contains a binder resin and a colorant as main components, and also includes a charge control agent, a release agent, and other necessary properties as a toner. It generally contains additives. As a colorant for the magnetic toner, a magnetic material is used as it is as a colorant, or carbon black or a non-magnetic inorganic compound, an organic pigment, a dye, or the like is used together with the magnetic material.As the release agent, low molecular weight polyethylene,
A material that is hardly compatible with the binder resin, such as low molecular weight polypropylene, is used.

The purpose of using the release agent is to prevent a toner having good fixability on a transfer-receiving member from adhering to the surface of the fixing member. In recent years, printers have been operating at higher speeds, and as a result, there has been a demand for further lowering the temperature of the toner, and accompanying this, a great deal of effort has been made to improve the adhesion of the toner to the fixing member surface, that is, the so-called offset. Have been paid. Incorporation of a wax as a release agent in a toner is disclosed in, for example, JP-B-52-3304 and JP-B-52-304.
The technology is disclosed in Japanese Patent Application Laid-Open No. 3305, Japanese Patent Application Laid-Open No. 57-52574, and the like.

Also, JP-A-3-50559, JP-A-2-79860, JP-A-1-109359, JP-A-62-14166, and JP-A-61-27
3554, JP-A-61-94062, JP-A-61-138259, JP-A-60-25236
No. 1, Japanese Unexamined Patent Publication No. 60-252360, Japanese Unexamined Patent Publication No.
Japanese Patent Application Laid-Open No. 0-217366 discloses a technique for containing waxes.

However, as described above, since the release agent generally has poor compatibility with the binder resin, it is relatively difficult to uniformly disperse the release agent in the toner. In this case, the charge amount of the toner becomes non-uniform, and it is not easy to achieve high image quality and high durability without contamination of non-image portions such as fog. Furthermore, the toner fluidity is deteriorated and the charge amount of the toner becomes more uneven, and when the toner is exposed to the toner at a high temperature for a long time, the wax migrates to the toner surface, and the developability and transferability are further deteriorated. I do.

On the other hand, in a developing method using an insulating magnetic toner, there are unstable factors related to the insulating magnetic toner to be used. One 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. And influences the triboelectrification, and as a result, causes fluctuation or deterioration of various characteristics required for the magnetic toner, such as development characteristics, transferability, and durability of the magnetic toner.

It is considered that the above-mentioned problem is caused when a magnetic toner containing a conventional magnetic material is used, because 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, the deterioration of the toner such as a decrease in the image density due to the separation of the magnetic material due to the rubbing between the toners or the toner layer thickness regulating member or the occurrence of uneven density called a sleeve ghost is caused. These problems are particularly prominent under high humidity where the triboelectric charge is apt to decrease.

Still another unstable factor is the dispersibility of the magnetic material. That is, ideally, it is desirable that the magnetic substance content of each toner particle and the dispersion state inside the particle are uniform, but generally, the binder resin for toner composed of an organic substance or the release agent and the inorganic substance are used. In reality, it is almost impossible to completely disperse the magnetic substance completely uniformly because of its poor familiarity with the magnetic substance, the difference in specific gravity and the magnetic aggregation. If the dispersion of the magnetic material inside the toner particles is poor, the dispersion state of the release agent becomes uneven along with the dispersion.

Further, as described above, as the direction of recent technology, a higher resolution and higher definition developing method has been demanded, and in order to respond to such a demand, the toner particle size has been reduced. As the toner particle size becomes smaller, uniform dispersion of the material becomes an important technique. That is, unless a uniform amount of the magnetic material and the release agent is contained in a uniform state in the individual fine toner particles, the image characteristics and the stability thereof tend to be more remarkably reduced. This is simply because the particle size of the toner becomes smaller, and the adhesion force (mirror image force, van der Waals force, etc.) of the toner particles to the photoreceptor is larger than the Coulomb force applied to the toner particles in the transfer process. As a result, in addition to an increase in transfer residual toner, a decrease in toner diameter is unavoidably accompanied by an increase in charge amount and deterioration in fluidity, so that a difference in dispersibility tends to appear as a large physical property difference, This is because the ratio of fog and toner having poor transferability increases.

Conventionally, magnetic iron oxide has been proposed as a magnetic substance contained in a magnetic toner, but there is still a point to be improved. For example, Japanese Patent Application Laid-Open
279352 proposes a magnetic toner containing a magnetic iron oxide containing a silicon element. 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.

Further, Japanese Patent Publication No. 3-9045 proposes to control the shape of a magnetic iron oxide to be spherical by adding a silicate. 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.

Japanese Unexamined Patent Publication (Kokai) No. 61-34070 proposes a method for producing iron sesquioxide by adding a hydrososilicate solution during the oxidation reaction to iron sesquioxide.
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 limitation 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.

Further, in the pulverization method, it is difficult to completely and uniformly disperse solid fine particles such as a magnetic substance or a colorant and a release agent having low compatibility in a resin. Increases and the image density decreases.
Furthermore, the pulverization method essentially exposes the magnetic material and the release agent to the surface of the toner, and thus leaves a problem in terms of the fluidity of the toner and the charging stability under severe environments such as high humidity. 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 along with this, the powder characteristics, particularly the uniform charging property 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.

In this suspension polymerization method, since a droplet of the monomer composition is formed in a dispersion medium having a large polarity such as water, the component having a polar group contained in the monomer composition is an aqueous phase. A so-called core / shell structure in which a non-polar component does not easily exist in the surface layer portion, which is likely to be present in the surface layer portion at the interface with, can be formed. That is, in general, a toner produced by a polymerization method completely suppresses the influence of wax on the toner surface while maintaining low-temperature fixability and high-temperature offset resistance inside the toner by incorporating a low-polarity release agent component. Enables ideal toner design. However,
By simultaneously containing a magnetic material and a release agent in this polymerized toner, its fluidity and charging characteristics are significantly reduced. One reason is that the magnetic particles are generally hydrophilic and thus easily exist on the toner surface, and the other is that the magnetic particles are formed inside the toner particles due to a difference in specific gravity or magnetic aggregation. This is because the mold release agent tends to be unevenly distributed, and the release agent is also likely to be unevenly distributed. In an extreme case, the magnetic material may be present in one half of the toner particles and the release agent may be present in the other half. If the magnetic material is unevenly distributed in the center of the toner particles, the release agent is repelled to the outside of the particles and is exposed on the toner surface. Leads to worse sex. Further, if a releasing agent having a low melting point is used for the purpose of fixing at a low temperature, the blocking resistance, that is, the toner cohesiveness at the time of standing is deteriorated.

In order to solve this problem and exert the merits of the polymerization method toner, it is important to improve the surface properties of the magnetic substance and to improve the physical properties such as compatibility with organic substances. Many proposals have been made regarding surface modification for improving the dispersibility of a magnetic substance in a polymerized toner. For example, JP-A-59-200254 and JP-A-59-200256
JP, JP-A-59-200257, JP-A-59-200257
Japanese Unexamined Patent Publication (Kokai) No. 63-250 proposes various techniques for treating a magnetic substance with a silane coupling agent.
660 and JP-A-10-239897,
A technology for treating silicon element-containing magnetic particles with a silane coupling agent has been disclosed.

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.
In addition, when a release agent is used at the same time, the dispersibility of the release agent is adversely affected as described above.

As an example of using a hydrophobic magnetic iron oxide, Japanese Patent Publication No. 60-3181 proposes a toner containing a magnetic iron oxide treated with an alkyl trialkoxysilane. Although the electrophotographic properties of the toner have certainly been improved by the addition of this magnetic iron oxide, the surface activity of the magnetic iron oxide is originally small, and coalesced particles are generated at the processing stage, and the hydrophobicity is uneven. Is not always satisfactory.

As described above, in the conventional surface-treated magnetic material,
For use in a polymerized toner containing a release agent, compatibility between hydrophobicity and material dispersibility has not necessarily been achieved, and even if a polymerized toner is manufactured using such a magnetic material, a toner having excellent performance can be obtained. It is difficult.

On the other hand, apart from such a toner production method or a material dispersion method, a method of adding inorganic fine particles as an external additive to toner base particles for the purpose of improving the flow characteristics and charging characteristics of the toner has been proposed. Used.

For example, inorganic fine particles subjected to a hydrophobizing treatment as disclosed in JP-A-5-66608, JP-A-4-9860, etc., or inorganic fine particles treated with a silicone oil or the like after the hydrophobizing treatment are added, or Kaisho 61-
249059, JP-A-4-264453,
Japanese Patent Application Laid-Open No. 5-346682 discloses a method in which hydrophobically treated inorganic fine particles and silicone oil-treated inorganic fine particles are added in combination.

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. Also, JP-A-57-151952, JP-A-59-168458 and JP-A-60-6
No. 9660 discloses that conductive fine particles of tin oxide, zinc oxide and titanium oxide are externally added to a high-resistance magnetic toner. Also, JP-A-56-142
No. 540 discloses that 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, thereby achieving both developability and transferability. Furthermore,
JP-A-61-275864, JP-A-62-258
472, JP-A-61-141452, and JP-A-2-120865 disclose adding graphite, magnetite, polypyrrole conductive particles, and polyaniline conductive particles to a toner.
It is known to add a wide variety of conductive fine particles to toner.

However, these improvements are not sufficiently effective for toners having poor material dispersibility.

Now, from the viewpoint of compactness or ecology of the apparatus as described above, in recent years, 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 is disclosed in Japanese Unexamined Patent Publication No.
As described in Japanese Patent No. 2287, the main focus is on a positive memory, a negative memory, and the like due to the influence of residual toner on the image. However, with the advance of the use of electrophotography, there is a need to transfer toner images to various recording media, and in this sense, it has not been satisfactory for various recording media.

JP-A-59-133573, JP-A-62-203182, and JP-A-63-133179 disclose technologies related to cleanerless.
Gazette, JP-A-64-20587, JP-A-2-3
JP-A-02772, JP-A-5-2289, JP-A-5-53482, JP-A-5-61383, etc., but there is no description of a desirable image forming method, and the toner composition is also mentioned. Not.

As a development method which is preferably applied to simultaneous development cleaning or cleanerless, conventionally, development simultaneous cleaning essentially having no cleaning device includes:
Since a structure in which the surface of the image carrier is rubbed with the toner and the toner carrier has been essential, many contact development methods in which the toner or the toner comes into contact with the image carrier have been studied. This is to collect the transfer residual toner in the developing means,
This is because a configuration in which the toner or the toner contacts and rubs against the image carrier is considered to be advantageous. However, simultaneous development cleaning or a cleanerless process to which the contact development method is applied causes deterioration of the toner, deterioration of the surface of the toner carrier, deterioration of the surface of the photoreceptor or wear due to long-term use, and a sufficient solution to the durability characteristics. Not.
Therefore, a simultaneous cleaning method using a non-contact developing method has been desired.

In an image forming method used for an electrophotographic apparatus or an electrostatic recording apparatus, various methods for forming a latent image on an image carrier such as an electrophotographic photosensitive member or an electrostatic recording dielectric are also used. It has been known.

For example, in the electrophotographic method, a photoreceptor using a photoconductive substance as an image carrier is uniformly charged to a required polarity and potential, and then subjected to image pattern exposure to obtain an electric latent image. A method of forming an image is common.

Heretofore, a corona charger (a corona discharger) has been often used as a charging device for uniformly charging (including a charge removing process) an image carrier to a required polarity and potential. The corona charger is a non-contact type charging device, and includes a discharge electrode such as a wire electrode and a shield electrode surrounding the discharge electrode. 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 bearing member, 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 a corona charger. 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 other conductive charging member (contact charging member / contact charging device). ) 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), there are two types of charging mechanisms, a discharge charging mechanism and a direct injection charging mechanism, and each characteristic appears depending on which one is dominant. Discharge Charging Mechanism This is a mechanism in which the surface of the member to be charged is 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. 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 in which the contact member comes into contact with the member to be charged more frequently, it is necessary to provide a structure in which the contact charging member has a denser contact point and has a large speed difference from the member to be charged.

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

The charging mechanism in the conventional roller charging is dominated by the discharge charging mechanism. 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 friction roller has a large frictional resistance and is often driven by the member to be charged or driven with a slight speed difference. You. 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. 2 is a graph showing an example of charging efficiency of contact charging in electrophotography. The horizontal axis represents the bias applied to the contact charging member, and the vertical axis represents the charging potential (hereinafter, referred to as a photoreceptor) charging potential 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 charging to -500 V, a DC voltage of -1000 V is applied, or an AC voltage of 1200 V between peaks is applied so as to always have a potential difference equal to or greater than the discharge threshold in addition to the charging voltage of -500 V DC. In general, the potential of the photosensitive member is converged to the charged potential. 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 starts to increase when a voltage of about 640 V or more is applied, and Thereafter, the photoconductor surface potential linearly increases with a slope of 1 with respect to the applied voltage. 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 Vd + Vth
Therefore, a DC voltage higher than required is 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 DC charging, 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 photoreceptor. Difficult to value.

For this reason, as disclosed in Japanese Patent Application Laid-Open No. 63-149669, a DC voltage corresponding to a desired Vd has a peak-to-peak voltage of 2 × Vth or more, as disclosed in JP-A-63-149669. An “AC charging method” in which a voltage on which an AC component is superimposed is applied to a contact charging member is used. 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, the essential charging mechanism uses a discharge phenomenon from the contact charging member to the photosensitive member, so that the voltage 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 photosensitive member due to the electric field of the AC voltage, and discharge due to discharge. Deterioration of the surface of the photoreceptor becomes remarkable, and this is a new problem. Further, in the fur brush charging, a member having a brush portion of a conductive fiber (fur brush charger) is used as a contact charging member, and the conductive fiber brush portion is brought into contact with a photoreceptor as a member to be charged, and a predetermined charging is performed. A bias is applied to charge the photoreceptor surface to a predetermined polarity and potential. In the fur brush charging, the charging mechanism is dominated by the discharge charging mechanism.

As the fur brush charger, a fixed type and a roll type are in practical use. A fixed type is formed by folding a medium-resistance fiber into a base fabric and forming it in a pile shape and bonding it 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.
In order to perform sufficiently uniform charging by direct injection charging, it is necessary to provide a photoconductor with a speed difference that is 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. 2B. 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. Particle size of 5 to 50 μm as conductive magnetic particles constituting the magnetic brush portion
m, and by providing a sufficient speed difference with the photoconductor,
Uniform direct injection charging is possible. As shown by C in the charging characteristic graph of FIG. 2, it is possible to obtain a charging potential substantially proportional to the applied bias. 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.

Here, it is assumed that these contact charging methods are applied to the 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 photoreceptor due to the absence of the cleaning member (including the fog toner remaining without being transferred due to the polarity opposite to the transfer bias). Is)
However, as it comes into contact with the contact charging member, it 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 lowers the contrast and the uniformity of the electrostatic latent image after image exposure, and lowers the image density or increases fog.
In the simultaneous cleaning method and the image forming method, the charge polarity and the charge amount of the transfer residual toner on the photosensitive member are controlled, and the toner on the photosensitive member is stably collected in the developing process. The point is to prevent the 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 step, an image visualized by a positive polarity transfer member is transferred to a recording medium. However, depending on the relationship between the type of recording medium (differences in thickness, resistance, dielectric constant, etc.) and the image area, the charge polarity of the transfer residual toner varies from plus to minus. In the non-image area, fog toner of the opposite polarity generated due to non-uniformity of toner charge amount is developed. However, due to the negative polarity charging member when charging the negatively chargeable photoreceptor, even if the residual toner along with the photoreceptor surface fluctuates to a positive polarity in the transfer process, or fog toner having the opposite polarity originally. However, the charging polarity can be evenly adjusted to the negative side. Therefore, when the reversal development is used as the developing method, the negatively charged transfer residual toner remains in the bright portion potential portion of the toner to be developed, and the developing portion is not developed in the dark portion potential where the toner is not to be developed. Due to the electric field, the toner is attracted toward the toner carrier, and the toner is collected without remaining on the photoconductor having the dark portion potential. That is, by controlling the charging polarity of the toner on the photoconductor at the same time as the charging of the photoconductor by the charging member, the simultaneous cleaning with development and the cleanerless image forming method are realized.

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 toner cannot be made uniform, and the toner is removed by the developing member. It becomes difficult to collect. Also, even if the collected toner is collected on the toner carrier, if the charge of the collected toner is not uniform,
This adversely affects the chargeability of the toner on the toner carrier, and deteriorates the developing characteristics. Further, when a toner having poor material dispersibility is used, the poor toner accumulates in the developing device as the toner is used for a long period of time, resulting in a remarkable deterioration in image characteristics.

That is, in the simultaneous development cleaning and cleanerless image forming method, the uniform dispersion of the magnetic material and the release agent in the toner particles, the toner performance such as developability and transferability, the transfer residue, Charging control characteristics of toner passing through the charging member and adhesion / mixing characteristics to the charging member
It is closely linked to image characteristics and durability characteristics.

Japanese Patent Publication No. 7-99442 discloses a configuration in which a powder is applied to a contact charging member with a contact surface with a surface to be charged in order to prevent charging unevenness and perform stable uniform charging. However, contact charging member (charging roller)
Is driven by a member to be charged (photoreceptor) (no speed difference drive), and the generation of ozone products is much less than that of a corona charger such as a scorotron. As in the case of the above, the discharge charging mechanism is mainly used as before. 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 cleaner-less image forming apparatus, it becomes difficult for the applied powder to uniformly adhere to the charging member due to the incorporation of transfer residual toner, and the effect of performing uniform charging is weakened.

Japanese Patent Application Laid-Open No. HEI 5-150539 discloses that, in an image forming method using contact charging, toner particles and silica fine particles which cannot be completely cleaned by blades during repeated image formation on the surface of the charging means. It is disclosed that the toner contains at least visible particles and conductive fine particles having an average particle size smaller than the visible particles in order to prevent charging inhibition due to adhesion and accumulation. 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 step, and the effect of the recovered conductive fine particles and the recovered 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.

Japanese Patent Application Laid-Open No. H11-15206 discloses a method of forming an image with simultaneous cleaning by improving the simultaneous cleaning with development by improving the charge control characteristic of the residual toner after passing through the charging member. ,
An image forming method using a toner having toner particles containing a specific carbon black and a specific azo-based iron compound and inorganic fine powder has been proposed. 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, and a simultaneous cleaning for development which assists or controls the recovery of residual 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, Japanese Patent Application Laid-Open No. H10-307456 discloses
Patent Document 1: Japanese Patent Application Publication No. JP-A-2005-17764, an image forming apparatus applied to a simultaneous developing image forming method using a direct injection charging mechanism using 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 disclosed. According to this proposal, without producing discharge products,
It is possible to obtain a low cost, simultaneous development and simultaneous cleaning image forming apparatus capable of greatly reducing the amount of waste toner, and to obtain a good image free from poor charging, light blocking or diffusion of image exposure.

Japanese Unexamined Patent Publication (Kokai) No. 10-307421 discloses a simultaneous cleaning image formation using a direct injection charging mechanism for toner containing conductive particles having a particle diameter of 1/50 to 1/2 of the toner particle diameter. There is disclosed an image forming apparatus which is applied to a method and in which conductive particles have a transfer promoting effect.

Further, Japanese Patent Application Laid-Open No. 10-307455 discloses that the particle size of the conductive fine powder is set to be equal to or less than the size of one pixel constituting the pixel, and the particle size of the conductive fine powder is obtained in order to obtain better charging uniformity. It is described that the diameter is 10 nm to 50 μm.

In Japanese Patent Application Laid-Open No. H10-307457, conductive particles are reduced by about 5 in order to make it difficult to visually recognize the influence of a poorly charged portion on an image in consideration of human visual characteristics.
It is described that it is not more than μm, preferably 20 nm to 5 μm.

According to JP-A-10-307458, the particle size of the conductive fine powder is set to be equal to or smaller than the toner particle size, thereby hindering the development of the toner at the time of development, or the developing bias is applied to the conductive fine powder. The fine particles of the conductive fine particles are set to be larger than 0.1 μm so that the fine conductive particles can be embedded in the image carrier to prevent exposure light. A method of forming an image simultaneously with development using a direct injection charging mechanism that also solves the problem of light shielding and realizes excellent image recording is described.

According to Japanese Patent Application Laid-Open No. 10-307456, a conductive fine powder is externally added to a toner, and at least a conductive portion contained in the toner is provided at an abutting portion between a contactable charging member and an image carrier. The fine powder adheres to the image carrier in the developing process and remains on the image carrier after the transfer process, and is carried and interposed. Is disclosed.

However, these proposals also have room for further improvement in the 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. Moreover, these effects are limited unless the performance of the toner particles themselves is involved.

[0073]

SUMMARY OF THE INVENTION An object of the present invention is to provide a toner and an image forming method which solve the above-mentioned problems of the prior art. That is, an object of the present invention is to provide a toner having stable charging performance and image characteristics regardless of the environment.

Another object of the present invention is to provide a toner and an image forming method having stable image characteristics even when used for a long time in a high temperature environment.

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

An object of the present invention is to make it possible to form a cleaning image at the same time as development, which can reduce the amount of waste toner significantly without generating discharge products, which is advantageous in miniaturization at low cost, and which can be repeated for a long period of time. An object of the present invention is to provide a method of forming an image at the same time as developing, which can stably obtain a good image free from poor charging even when used, and a toner used therefor.

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

Another object of the present invention is to provide a toner and an image forming method which are capable of forming a cleaning image at the same time as development, which is excellent in transferability and excellent in recovering residual toner after transfer.

An object of the present invention is to provide a simultaneous cleaning image forming method capable of stably obtaining a good image even when toner particles having a small particle size are used to enhance the resolution, and a toner used therefor. Is to do.

[0080]

As described above, the state of dispersion of the magnetic substance and the release agent inside the toner particles greatly affects the toner performance. This is an important technology. Further, if the transferability and fog characteristics of the toner can be further improved, it is possible to easily achieve long-term maintenance of high image quality even in an environmentally preferable contact charging method with less generation of ozone and a cleanerless image forming method.

The inventors of the present invention have conducted various studies on the physical properties and materials of the magnetic toner. As a result, the magnetic toner contained a magnetic substance which was well dispersed in a hexane solution, and the magnetic substance was substantially exposed on the surface. The magnetic toner having an average circularity of 0.970 or more has a very uniform dispersion state of the magnetic substance and the release agent inside the toner, and as a result, has excellent blocking resistance and high transferability. , Good fog characteristics, and excellent developability. Further, even under a high temperature at which the developing property is reduced due to the release agent exposed on the toner surface, the transfer residual toner is increased, or the durability is likely to be reduced, the developing property is good, and the high It was possible to obtain a high-quality image for a long time. Furthermore, it has been found that by using this type of magnetic toner, a long-term maintenance of a high-quality image can be achieved even in an environmentally preferable contact charging method and further in a cleanerless image forming method. It was completed.

That is, the present invention is as follows.

According to the present invention, there is provided a magnetic toner having an inorganic fine powder on the surface of magnetic toner particles having at least a binder resin, a release agent and a magnetic material, wherein the magnetic toner has an average circularity of 0.970 or more. , The weight average particle diameter (D4) is 3 to 10 μm, the magnetic toner particles contain magnetic iron oxide as the magnetic substance, and the magnetic toner has a magnetic field of 79.6 kA / m (1000 Oersted). The magnetization intensity is 10 to 50 Am ² / kg (emu /
g), in the dispersion state in a hexane solution, the magnetic substance has an absorbance at 500 nm after 5 minutes from the dispersion at a-5 and 500 n after 30 minutes from the dispersion.
When the absorbance at m is a-30, a-5, a-3
0 satisfies the following expression (1).

[0084]

0.8 <a−30 / a−5 Equation (1) Further, the present invention provides a charging step of applying a voltage to a charging member to charge an image carrier, and applying a voltage to the charged image carrier. An electrostatic latent image forming step of forming an electrostatic latent image, the image carrier,
A toner carrier for supporting the magnetic toner on the surface is arranged at a predetermined interval, and the magnetic toner is coated on the surface of the toner carrier to a thickness smaller than the interval, and an AC voltage is applied. A developing step of developing the toner image by transferring the magnetic toner to the electrostatic latent image in a developing unit; and a transfer step of electrostatically transferring the toner image formed on the image carrier to a transfer material. In the image forming method, the toner on the toner carrier in the developing step is the magnetic toner of the present invention.

Further, according to the present invention, there is provided an image carrier for carrying an electrostatic latent image, charging means for applying a voltage to a charging member to charge the image carrier, and charging the image carrier.
Electrostatic latent image forming means for forming an electrostatic latent image; and transferring the toner image on the image carrier by transferring the magnetic toner carried on the toner carrier to the electrostatic latent image formed on the image carrier. A developing unit for forming the toner image on the surface of the image carrier, a transferring unit for electrostatically transferring the toner image formed on the surface of the image carrier to a transfer material, and a fixing unit for fixing the toner image on the transfer material. A process cartridge configured to be capable of supporting at least one unit selected from the group consisting of the image carrier and the charging unit, the unit being integrally supported with the developing unit, and being supported on the toner carrier. The toner thus obtained is the process cartridge according to the present invention.

[0086]

DESCRIPTION OF THE PREFERRED EMBODIMENTS <1> Magnetic Toner of the Present Invention The magnetic toner of the present invention is a toner having an inorganic fine powder on the surface of magnetic toner particles having at least a binder resin, a release agent and a magnetic substance.

The binder resin used in the magnetic toner of the present invention includes the following when the magnetic toner is produced by a pulverizing method.

When the toner of the present invention is produced by a pulverization method, the binder resin may be, for example, a homopolymer of styrene such as polystyrene and polyvinyltoluene and a substituted product thereof; a styrene-propylene copolymer and a styrene-vinyltoluene copolymer. Copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-acrylic acid Dimethylaminoethyl copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-dimethylaminoethyl methacrylate copolymer, styrene- Vinyl methyl ether copolymer, styrene-vinyl Styrene copolymers such as ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-maleic acid copolymer, and styrene-maleic acid ester copolymer Polymers: polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyethylene, polypropylene, polyvinyl butyral, silicone resin, polyester resin, polyamide resin, epoxy resin, polyacrylic resin, rosin, modified rosin, tempel resin, phenol resin, Aliphatic or alicyclic hydrocarbon resins, aromatic petroleum resins, paraffin wax, carnauba wax and the like can be used alone or in combination. In particular, styrene-based copolymers and polyester resins are preferred in terms of development characteristics, fixability, and the like.

When the toner of the present invention is produced by a suspension polymerization method, the following polymerizable monomers constituting the polymerizable monomer system may be used.

Examples of the polymerizable monomer include styrene monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, and p-ethylstyrene, and methyl acrylate and acrylic. Ethyl acrylate, n-butyl acrylate, isobutyl acrylate, n-propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, etc. Acrylic esters, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate
Examples thereof include methacrylates such as 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, and diethylaminoethyl methacrylate, and monomers such as acrylonitrile, methacrylonitrile, and acrylamide. 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 particles of the present invention have a release agent. A wax is used as a release agent. 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 a Fischer-Tropsch method. Hydrocarbon waxes and derivatives thereof, polyolefin waxes represented by polyethylene and derivatives thereof, carnauba wax, natural waxes such as candelilla wax and derivatives thereof, etc., and derivatives include oxides and block copolymers with vinyl monomers, Including 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 magnetic toner of the present invention contains a release agent. The amount of the release agent is preferably 0.5 to 50 parts by mass with respect to 100 parts by mass of the binder resin. If the content is less than 0.5 part by mass, the offset suppressing effect is poor,
If the amount exceeds 50 parts by mass, the storage stability for a long time is inevitably deteriorated, the dispersion state inside the toner becomes uneven, and it is difficult to suppress the exposure to the toner surface.
It is not preferable because it leads to deterioration of the fluidity of the toner and deterioration of image characteristics and durability.

Among the above wax components, the DSC curve measured by a differential scanning calorimeter indicates that the wax component is 40
Those having a maximum endothermic peak in the region of to 110 ° C are preferable, and those having the maximum endothermic peak in the region of 45 to 90 ° C are more preferable. By having the maximum endothermic peak in the above temperature range, it greatly contributes to low-temperature fixing, and also effectively expresses the 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 tends to 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. .

The maximum endothermic peak temperature of the wax component is measured according to “ASTM D 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.

Further, by using the toner as a measurement sample, the endothermic peak area attributed to the wax, that is, the amount of heat absorbed by the wax in the toner is determined, and the wax content in the toner is compared with that of a sample whose wax content is known. The wax content can be determined.

The magnetic material used in the magnetic toner of the present invention mainly comprises magnetic iron oxide. More specifically, in a dispersion state in a hexane solution, a-5 represents the absorbance at 500 nm after 5 minutes from the dispersion, and a-30 represents the absorbance at 500 nm after 30 minutes from the dispersion. 5. Use a magnetic material such that a-30 satisfies the following formula (1).

[0097]

0.8 <a−30 / a−5 Formula (1) Further, when the absorbance at 500 nm after elapse of 60 minutes after dispersion in a hexane solution is defined as a−60, a−
More preferably, a-60 is a magnetic material satisfying the following formula (2).

[0098]

0.8 <a−60 / a−5 Equation (2) In the case of a magnetic material satisfying a−30 / a−5 ≦ 0.8, that is, when the magnetic material is dispersed in a hexane solution, the sedimentation velocity is reduced. In the case of a fast magnetic material, it is difficult to uniformly disperse the toner particles inside the toner particles, and the dispersion state of the release agent may be uneven.

The magnetic material satisfying the above formula (1) includes iron trioxide, γ-, which may contain elements such as cobalt, nickel, copper, magnesium, manganese, and aluminum.
It is obtained by subjecting a material mainly composed of magnetic iron oxide such as iron oxide to a uniform surface treatment, and these are used alone or in combination of two or more in a toner.

As more preferable physical properties of the magnetic material, the absorption constant at 500 nm after 30 minutes from the dispersion in the hexane solution is preferably 1000 or more, and the absorption constant at 500 nm after 60 minutes from the dispersion is higher. 1
More preferably, it is 000 or more. If the extinction constant at 500 nm after 30 minutes from the dispersion in the hexane solution is less than 1000, it means that the dispersibility in an organic substance is not so good, and it is difficult to obtain a toner having higher coloring power. Not preferred.

In the present invention, the absorbance and the extinction constant of the magnetic substance in a dispersion state in a hexane solution can be measured as follows.

In the present invention, a Shimadzu self-recording spectrophotometer,
It is measured using UV-2200 (manufactured by Shimadzu Corporation) (the same applies to examples described later).

A magnetic material as a measurement sample is weighed. The mass at this time is assumed to be A1 kg. The weighed sample is placed in a sealable container. A hexane solution whose volume is weighed is added thereto, and the container is sealed. The volume of the hexane solution at this time is defined as B1. The sample concentration at this time is preferably about 0.0002 kg of magnetic substance per liter of hexane solution. After lightly shaking the container by hand, dispersion treatment is performed for 10 seconds by ultrasonic waves.

The obtained sample dispersion solution was placed at a light transmission distance of 1 cm.
Quickly set in the device in a quartz cell,
Five minutes after setting the cell, the absorbance at a wavelength of 500 nm is measured. The absorbance at this time is defined as a-5 of the magnetic substance.

The cell is allowed to stand in the apparatus as it is, and the absorbance at a wavelength of 500 nm is measured 30 minutes after setting the cell. The absorbance at this time is defined as a-30 of the magnetic substance. Similarly, 500 nm after 60 minutes of cell setting.
The absorbance at this wavelength is measured, and the absorbance at this time is defined as a-60 of the magnetic substance.

Next, the sample concentration A1 / B1 (kg / L) was calculated, and a-30 / (A1 / B1) was taken as the extinction constant at 500 nm 30 minutes after the dispersion, and a-60 /
500 nm after elapse of 60 minutes after (A1 / B1) dispersion
And the extinction constant.

The volume average particle diameter of the magnetic material is 0.1.
It is preferably from 0.5 to 0.3 μm, more preferably from 0.06 to 0.3 μm.
25 μm is more preferred. Volume average particle size is 0.05μm
If it is less than 1, the blackness is remarkably reduced, the coloring power of the black-and-white toner is insufficient, and the agglomeration of the magnetic particles becomes strong. There is. On the other hand, when the average particle size exceeds 0.3 μm, the mass per magnetic material particle becomes heavy, and the magnetic material tends to precipitate in a hexane solution, so that the dispersion state inside the toner particles becomes uneven. In addition, it becomes probabilistically difficult to disperse the same number of magnetic substances in individual toner particles, and the dispersibility tends to deteriorate.

The volume average particle diameter (Dm) of the magnetic material is as follows:
It can be measured using a transmission electron microscope. Specifically, a powder sample of the toner to be measured is observed with a transmission electron microscope at a magnification of 40,000, and the diameter of 100 magnetic particles having a size of 0.01 μm or more is measured in the visual field, and the average particle diameter is determined. Ask.
Since the presence of the magnetic particles having a particle size of less than 0.01 μm hardly affects the dispersion state of the release agent, and even if the toner particles are slightly exposed on the toner surface, they do not adversely affect triboelectric charging. In, basically, the effect can be ignored.

The particle shape of the magnetic material is preferably a hexahedron, an octahedron, or a tetrahedron polyhedron. The bulk of the magnetic material is higher than in the case of a spherical shape, and the cohesiveness is reduced, so that the dispersibility during toner production is further improved. The shape of such a magnetic material can be confirmed by SEM (scanning electron microscope) or the like. That is, S
The shape of the magnetic particles is observed by EM, and the shape having the largest particle number ratio is defined as the powder shape of the sample.

It is also preferable that the magnetic material used in the magnetic toner of the present invention is surface-treated with a coupling agent in an aqueous medium. When the surface is hydrophobized, it is very preferable to use a method in which the magnetic particles are dispersed in an aqueous medium to have a primary particle size and the surface treatment is performed while hydrolyzing the coupling agent. In this hydrophobizing method, the magnetic particles are less likely to coalesce than in the gas phase, and the repulsion between the magnetic particles by the hydrophobizing process acts, so that the magnetic material is almost in the state of primary particles. Surface treated.

The method of treating the surface of the magnetic substance while hydrolyzing the coupling agent in an aqueous medium does not require the use of a coupling agent that generates a gas such as chlorosilanes or silazanes. In the gas phase, 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 according to 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).

[0113]

## STR1 ## R _m SiY _n (I) [wherein, R represents a Arukookishi group, m represents an integer of 1 to 3, Y is an alkyl group, vinyl group, glycidoxy group,
It represents a hydrocarbon group such as a methacryl 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 methyltriethoxysilane. , Isobutyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane, hydroxypropyltrimethoxysilane, phenyltrimethoxysilane, n-hexadecyltrimethoxysilane,
and n-octadecyltrimethoxysilane.

In particular, the magnetic substance is preferably subjected to a hydrophobic treatment in an aqueous medium using an alkyl trialkoxysilane coupling agent represented by the general formula (II).

[0115]

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 substance from the toner particles. When p is larger than 20, the hydrophobicity becomes sufficient,
The coalescence of the magnetic particles increases, making it difficult to uniformly disperse the magnetic particles in the toner, and fogging, transferability, and selective developability tend to deteriorate.

When q is larger than 3, the reactivity of the silane coupling agent is reduced, and it becomes difficult to sufficiently effect hydrophobicity. In particular, alkyltrialkoxysilane in which p in the formula represents an integer of 2 to 20 (more preferably, an integer of 3 to 15) and q represents an integer of 1 to 3 (more preferably, an integer of 1 or 2) It is good to use a coupling agent.

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

Here, the aqueous medium is a medium containing water as a main component. Specifically, water itself as an aqueous medium, water with a small amount of a surfactant added,
Examples thereof include those in which a preparation agent is added and those in which an organic solvent is added to water. 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. Stirring is performed by, for example, 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 surface-treated magnetic material thus obtained, no aggregation of particles is observed, and the surface of each particle is uniformly subjected to a hydrophobic treatment.
The dispersibility in the toner particles is very good, and at the same time, the dispersibility of the release agent is dramatically improved. In addition, there is no exposure of the magnetic substance and the release agent from the surface of the toner particles, so that a substantially spherical polymerized toner can be obtained.

The magnetic properties of the magnetic material include a magnetic field of 79.6.
kA / m, saturation magnetization is 10 to 200 Am ² / kg, residual magnetization is 1 to 100 Am ² / kg, coercive force is 1 to 30 k
A / m is preferably used. The magnetic properties of the magnetic material were measured using a vibration magnetometer (VSM-3S manufactured by Toei Kogyo Co., Ltd.).
-15).

By using such a magnetic material, it is possible to obtain the magnetic toner of the present invention having an average circularity of 0.970 or more and substantially exposing no magnetic material or release agent on the surface. Further, a toner having a sharp particle size distribution such that D4 / D1 is less than 1.4 can be easily obtained. Furthermore, if this toner is used in the image forming method of the present invention,
High image quality can be stabilized even under high temperature or high humidity environment.

The magnetic material used in the toner of the present invention is preferably used in an amount of 10 to 200 parts by mass based on 100 parts by mass of the binder resin. 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 toner is poor, and it is difficult to suppress fog. Meanwhile, 2
When the amount is more than 00 parts by mass, 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. There is a tendency.

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

An alkali such as sodium hydroxide is added to the aqueous ferrous salt solution in an amount equivalent to or more than the iron component, and the aqueous solution is adjusted to be 0.05 to 5.0% by mass of phosphorus element with respect to iron element. Aqueous phosphorus compounds (eg, phosphates such as sodium hexametaphosphate and ammonium monophosphate, phosphates such as orthophosphates and phosphites) aqueous solutions, and sometimes 0 to 5.0 mass based on iron element. An aqueous solution of a water-soluble silicon compound (for example, water glass, sodium silicate, or potassium silicate) is added so as to have a silicon element content of 1% to prepare an aqueous solution containing ferrous hydroxide. Air is blown in while maintaining the pH of the prepared aqueous solution at pH 7 or more (preferably pH 7 to 10), and an oxidation reaction of ferrous hydroxide is performed while heating the aqueous solution to 70 ° C. or more to produce magnetic particles. .

At the end of the oxidation reaction, the pH of the solution was adjusted, the mixture was sufficiently stirred so that the magnetic iron oxide became primary particles, the coupling agent was added, and the mixture was sufficiently mixed and stirred. By lightly crushing, a surface-treated magnetic material can be 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 without passing through a drying step after the completion of the oxidation reaction, which is an important point for obtaining the magnetic toner 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 result of cleaning the surface of a steel sheet can be used. Further, iron chloride and the like can be used. is there.

The method for producing magnetic iron oxide by the aqueous solution method generally uses an iron concentration of 0.5 to 2 mol / l from the viewpoint of preventing an increase in viscosity 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. Further, in the reaction, as the amount of air is larger and the reaction temperature is lower, the particles are easily atomized. By using the surface-treated magnetic powder produced in this way, an excellent magnetic toner of the present invention can be obtained. In addition, by using such a magnetic toner in the image forming method of the present invention, the magnetic toner can be left in a severe environment. It is possible to achieve toner deterioration and high image quality under high humidity.

The magnetic toner of the present invention has an inorganic fine powder on the surface of the magnetic toner particles having the binder resin, the release agent and the magnetic material.

The toner of the present invention is also preferably used in which an inorganic fine powder having a number average primary particle diameter of 4 to 80 nm as a fluidizing agent is added in an amount of 0.1 to 4% by mass based on the whole toner. It is. The inorganic fine powder is added for improving the fluidity of the toner and making the toner base particles uniform in charge. However, the charge amount of the toner is adjusted and the environmental stability is improved by a treatment such as hydrophobizing the inorganic fine powder. It is also preferable to provide functions such as these.

The number average primary particle diameter of the inorganic fine powder is 80 nm.
If it is larger than this, good fluidity of the toner cannot be obtained,
The charge application to the toner particles is likely to be non-uniform, and in addition to the deterioration in developability, an increase in fog during durability, a decrease in image density,
There is a tendency that problems such as toner scattering cannot be avoided. When the average primary particle size of the inorganic fine powder is smaller than 4 nm, the cohesiveness of the inorganic fine powders is increased, and the aggregates have a wide particle size distribution with strong cohesiveness that is hard to be disaggregated by the disintegration treatment instead of the primary particles. , And image defects such as damage to the image carrier or toner carrier by the aggregates 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 powder should be 6
More preferably, it is ~ 35 nm.

When the amount of the inorganic fine powder is less than 0.1% by mass relative to the whole toner, the effect of improving the fluidity of the toner is reduced, and when it exceeds 4% by mass, the fixability of the toner is deteriorated. Tend to.

The number average primary particle diameter of the inorganic fine powder is a photograph of the toner magnified by a scanning electron microscope, and further contains the inorganic fine powder by elemental analysis means such as XMA attached to the scanning electron microscope. Measured by measuring 100 or more primary particles of inorganic fine powder adhering or releasing on the toner surface while comparing the photograph of the toner mapped with the element, and calculating the number average primary particle size I can do it.

The content of the inorganic fine powder can be quantified by X-ray fluorescence analysis using a calibration curve prepared from a standard sample.

As the inorganic fine powder to be added to the toner of the present invention, silica, alumina, titania and the like can be used.
For example, as the silica, both a so-called dry method produced by the vapor phase oxidation of a silicon halide or a so-called wet silica produced from water glass or the like, and dry silica called a fumed silica can be used. There are few silanol groups on the surface and inside the silica fine powder,
Further, dry silica having less production residue such as Na ₂ O and SO ₃ ^2- is more preferable. 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 inorganic fine powder is preferably subjected to a hydrophobizing treatment, particularly from the viewpoint of improving the characteristics under a high humidity environment. When the inorganic fine powder added to the toner absorbs moisture,
The charge amount of the toner is significantly reduced, and developability and transferability are likely to be deteriorated.

As the hydrophobizing agent for hydrophobizing the inorganic fine powder, silicone varnish, various modified silicone varnishes,
Examples include silicone oils, various modified silicone oils, silane compounds, silane coupling agents, and other treating agents such as organosilicon compounds and organotitanium compounds, which may be used alone or in combination.

Among these, treatment with silicone oil is preferred, and more preferred is treatment with silicone oil at the same time as or after the hydrophobic treatment of the inorganic fine powder. The use of the inorganic fine powder that has been subjected to such a hydrophobic treatment is advantageous in maintaining the charge amount of the toner particles high even under a high-humidity environment and reducing the selective developability.

The conditions for treating such inorganic fine powder include, for example, a silylation reaction with a silane compound or the like in the first step reaction to eliminate active hydrogen groups on the surface by chemical bonding, and then a silicone reaction in the second step reaction. The oil can form a hydrophobic thin film on the surface. The use amount of the silylating agent is preferably 5 to 50% by mass based on the inorganic fine powder. If it is less than 5% by mass, it is not sufficient to eliminate active hydrogen groups on the surface of the inorganic fine powder, and if it exceeds 50% by mass, a siloxane compound formed by a reaction between excess silylating agents serves as a glue and acts as a glue. Agglomeration of the powders occurs, which tends to cause image defects.

The above silicone oil preferably 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 powder has 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 a method for treating silicone oil,
For example, the inorganic fine powder silylated by a silane compound and silicone oil may be directly mixed using a mixer such as a Henschel mixer, or a method of spraying silicone oil onto the inorganic fine powder may be used. Alternatively, a method of dissolving or dispersing a silicone oil in an appropriate solvent, adding an inorganic fine powder, mixing and removing the solvent may be employed. A method using a sprayer is more preferable because the formation of aggregates of the inorganic fine powder is relatively small.

The processing amount of silicone oil was 1
1 to 23 parts by mass, preferably 5 to 20 parts by mass with respect to 00 parts by mass
Good mass parts. If the amount of the silicone oil is too small, good hydrophobicity cannot be obtained, and if it is too large, aggregation of the inorganic fine powder tends to occur.

The magnetic toner of the present invention can be further improved by using a conductive fine powder having a volume average particle diameter smaller than the volume average particle diameter of the toner in addition to the inorganic fine powder. It is preferable because it exhibits excellent image characteristics and durability.

It is considered that the reason for the addition effect is derived from the function of sharpening the triboelectric charge distribution of the toner. Since the toner of the present invention has substantially no magnetic material exposed on the surface, it cannot be said that the charge transfer is fast. For this reason, some toner particles have a low charge amount, and it cannot be denied that the toner particles are somewhat disadvantageous in terms of transferability and fogging. It is conceivable that when a conductive fine powder is added to the toner having such a configuration, an entropy-preferred uniform charge amount reaction such as charge transfer from a toner having a high charge amount to a toner having a low charge amount is likely to occur.

The content of the conductive fine powder in the whole toner is preferably 0.2 to 10% by mass. When the content of the conductive fine powder with respect to the whole toner is less than 0.2% by mass, the reaction rate for making the charge amount uniform under low humidity may not be sufficient. On the other hand, if it exceeds 10% by mass,
It becomes difficult to maintain a sufficient charge amount under high humidity, fog and transferability tend to decrease, and durability tends to deteriorate. Preferably, the content is 0.5 to 5% by mass. The preferable resistance of the conductive fine powder is 1 × 10 ⁹ Ω · cm or less. When the resistance of the conductive fine powder is larger than 1 × 10 ⁹ Ω · cm, the uniformization reaction rate tends to be insufficient. Further, when the density is 1 × 10 ⁶ Ω · cm or less, the distribution of the charge amount is extremely sharpened even under low humidity.

The volume average particle size of the conductive fine powder is 0.1 to 5
μm is preferred. Volume average particle size 0.1μ
If it is less than m, the effect of promoting the homogenization reaction rate is low. It is presumed that this is because the probability of the presence of the conductive fine powder in the contact portions between the toner particles is reduced, and the charge transfer from the high-charged toner to the low-charged toner is not so promoted.

The volume average particle diameter of the conductive fine powder is 5 μm.
If m is larger than m, the van der Waals force with the toner particles decreases, the toner particles are easily separated from the toner particles and easily adhere to the toner carrier, and the triboelectric charging of the toner tends to be inhibited. From these viewpoints, the volume average particle diameter of the conductive fine powder is preferably 0.15 μm or more, more preferably 0.2 μm or more and 4 μm or less, and a non-magnetic material for suppressing the adhesion to the toner carrier. It is preferred that

It is preferable that the conductive fine powder is a transparent, white or light-colored conductive fine powder, since the conductive fine powder transferred onto the transfer material is not conspicuous as fog. The conductive fine powder is preferably a transparent, white or light-colored conductive fine powder even in the sense that it does not hinder the exposure light in the latent image forming step. More preferably, the conductive fine powder has a transmittance to the exposure light of 30%. %.

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

The conductive fine powder according to the present invention is preferably non-magnetic, for example, carbon black,
Fine carbon powder such as graphite; fine metal powder such as copper, gold, silver, aluminum, nickel; zinc oxide, titanium oxide, tin oxide, aluminum oxide, indium oxide, silicon oxide, magnesium oxide, barium oxide, molybdenum oxide, and oxide Metal oxides such as iron and tungsten oxide; metal compounds such as molybdenum sulfide, cadmium sulfide, potassium titanate, and composite oxides thereof; and the like can be used by adjusting the particle size and particle size distribution as necessary. . Among them, 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, a metal oxide doped with an element such as antimony or aluminum, fine particles having a conductive material on the surface, or the like can be used. For example, titanium oxide fine particles surface-treated with tin oxide / antimony, stannic oxide fine particles doped with antimony, or stannic oxide fine particles.

Examples of commercially available conductive titanium oxide fine particles treated with tin oxide and antimony include, for example, EC-300.
(Titanium Industry Co., Ltd.), ET-300, HJ-1, H
I-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.). S (Japan Chemical Industry Co., Ltd.).

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

In the present invention, the method of adjusting the particle size and the particle size distribution of the conductive fine powder may be adjusted so that the primary particles of the conductive fine powder have a desired particle size and particle size distribution at the time of manufacture. In addition to the setting method, a method of aggregating small primary particles, a method of pulverizing large primary particles, or a method of classification can be used. A method of attaching or fixing the above-mentioned conductive particles to a part or all of the surface of the material particles, a method of 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 the like. It is also possible to adjust the particle size and particle size distribution of the conductive fine powder by combining these methods.

When the particles of the conductive fine powder are constituted as an aggregate, the particle size is defined as a volume average particle size as the aggregate. There is no problem that the conductive fine powder exists not only in the form of primary particles but also in the form of aggregated secondary particles. Regardless of the state of aggregation, any form can be used as long as the function of accelerating the reaction to homogenize the charge amount can be realized.

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

The magnetic toner of the present invention has 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 particle size) for the purpose of improving the cleaning property. Surface area is 50m ² / g
It is also one of the preferred embodiments to further add inorganic or organic fine particles having a spherical shape. For example, spherical silica particles, spherical polymethylsilsesquioxane particles, spherical resin particles and the like are preferably used.

A charge control agent may be added to the magnetic toner of the present invention in order to stabilize 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 toner is produced by a direct polymerization method, a charge control agent having a low polymerization inhibitory property and substantially having no soluble matter in an aqueous dispersion medium is particularly preferable.
As specific compounds, salicylic acid, alkyl salicylic acid, dialkyl salicylic acid as a negative charge control agent,
Naphthoic acid, a metal compound of an aromatic carboxylic acid such as dicarboxylic acid, a metal salt or a metal complex of an azo dye or an azo pigment, a polymer compound having a sulfonic acid or carboxylic acid group in a side chain, a boron compound, a urea compound, Silicon compounds, calixarenes and the like can be mentioned. Examples of the positive charge control agent include a quaternary ammonium salt, a polymer compound having the quaternary ammonium salt in a side chain, a guanidine compound, a nigrosine compound, and an imidazole compound. The charge control agent is added in an amount of 0.5 to 100 parts by mass of the binder resin.
It is preferable to use 10 to 10 parts by mass. However,
It is not essential to add a charge control agent to the magnetic toner of the present invention, and it is necessary to include the charge control agent in the toner by positively utilizing the frictional charge between the toner layer thickness regulating member and the toner carrier. There is no.

The magnetic toner of the present invention can also contain a colorant. As the colorant, the above-mentioned magnetic substance alone may be used as a coloring material, but a magnetic or non-magnetic inorganic compound, a known dye And pigments and the like. 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.

The magnetic toner used in the present invention may further contain other additives, for example, lubricant powders such as Teflon (registered trademark) powder, zinc stearate powder, and polyvinylidene fluoride powder within a range that does not substantially adversely affect the toner. Or abrasives such as cerium oxide powder, silicon carbide powder and strontium titanate powder; or fluidity imparting agents such as titanium oxide powder and aluminum oxide powder; anti-caking agents; and organic fine particles and inorganic fine particles of opposite polarity. Can be used in a small amount as a developing property improver. These additives can be used after the surface is subjected to a hydrophobic treatment. <
2> Characteristics of Magnetic Toner of the Present Invention The average circularity of the magnetic toner of the present invention is 0.970 or more. Average circularity is 0.9
A magnetic toner of 70 or more is extremely excellent in fog characteristics and transferability. The reason for this is that the magnetic toner forms fine spikes in the developing section due to the extremely high circularity, and the individual toner particles are uniformly charged, so that the variation in the amount of charge causing fog is small. It is conceivable that the contact area between the particles and the photoreceptor is small and the toner particles are easily transferred because the adhesion force of the toner particles to the photoreceptor due to the image force, Van der Waals force and the like is reduced.

At this time, in the circularity distribution of the toner, the mode circularity is more preferably 0.99 or more.
When the mode circularity is 0.99 or more, it means that most of the toner particles have a shape close to a true sphere, and the above-described action becomes more remarkable, and the fog characteristics and transferability are further improved.

In the present invention, the average circularity is used as an index for quantitatively expressing the shape of a particle. 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 equation (3), and a value obtained by dividing the total circularity of all particles measured by the following equation (4) by the total number of particles (m) is defined as an average circularity (am). Define.

[0164]

Circularity (ai) = L ₀ / L Equation (3) (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.)

[0165]

(Equation 8) 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 used in the present invention, “F
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.

A dispersion was prepared by dispersing about 5 mg of the magnetic toner in 10 ml of water in which about 0.1 mg of a surfactant was dissolved. The dispersion was 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 is measured only for particles having a circle equivalent diameter of 3 μm or more in this measurement is as follows.
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 magnetic toner of the present invention is characterized in that the magnetic substance is not substantially exposed on the toner surface. Therefore, unlike the normal toner obtained by the pulverizing method, the charge amount of the toner is hardly leaked. For example, it is possible to obtain a good image having a high image density under high humidity.

In the case where the spherical toner is reduced in diameter and a release agent is further contained to achieve higher resolution while maintaining good fixing properties, the dispersion state of the release agent is controlled. Is also an important technology.

However, as described above, the simultaneous use of the magnetic substance and the release agent tends to cause a bias in the material dispersion inside the toner particles, and it is difficult to suppress the exposure of the release agent to the toner surface. And various adverse effects occur. In particular, as the particle size of the toner becomes smaller, the adverse effect becomes more remarkable.

Therefore, the magnetic toner of the present invention is characterized by using the above-mentioned magnetic substance which is well dispersed in a hexane solution. A magnetic substance which is uniformly dispersed in a hexane solution and has a low sedimentation speed is also well dispersed in a binder resin, and does not cause aggregation or the like during toner production. Since such a magnetic material can be uniformly dispersed without deviation even inside the toner particles, the release agent present at the same time can be uniformly present inside the toner particles and is hardly exposed to the toner surface. For this reason, a small particle size magnetic toner of the present invention having a very good balance between the fixing property and the blocking resistance, good transferability and developability even at a high temperature, and excellent in developability can be obtained.

The magnetic properties of the magnetic toner containing such a magnetic substance are such that the magnetization intensity in a magnetic field of 76.9 kA / m (1000 Oe) is 10 to 50 Am ² / m.
kg (emu / g). 10 Am ² / kg (emu
/ G), it is difficult to sufficiently improve the fog characteristics even if the triboelectric characteristics can be improved by the shape of the toner, and the magnetic toner utilizing magnetic force may not be sufficient. On the other hand, if it exceeds 50 Am ² / kg (emu / g), the developability also tends to decrease.

The magnetic properties of the magnetic toner are the same as those of the magnetic material, and the vibration type magnetometer (VSM-3S- manufactured by Toei Kogyo KK) is used.
15) can be measured.

The present inventors have studied that, when a magnetic toner as described above is used to produce a small-diameter magnetic toner having a weight average particle diameter of 3 to 10 μm, a finer latent image dot can be faithfully formed. Since development was possible, the effect of improving image characteristics was remarkable. When the weight average diameter of the toner is less than 3 μm, it is difficult to avoid a decrease in transfer efficiency even when the above-described magnetic material is used, and it is difficult to uniformly charge the individual toner particles. Tends to be difficult. On the other hand, if the weight average diameter of the toner is more than 10 μm, characters and line images are liable to be scattered, and it is difficult to obtain high resolution. More preferably, the weight average particle diameter of the magnetic toner is 4
９9 μm.

At this time, the weight average particle size (D
It is more preferable that the ratio D4 / D1 of 4) to the number average particle diameter (D1) is less than 1.4 for the balance between the resolution of the toner, the transfer efficiency, and the effect of improving fog suppression. Even when the weight average diameter of the toner is 3 μm or more, if D4 / D1 is 1.4 or more, the ratio of toner particles having a small particle size in the particle size distribution is large, so that a decrease in transfer efficiency and deterioration of fog are avoided. Is difficult.

Here, the average particle size of the toner can be measured by various methods such as Coulter Counter TA-II or Coulter Multisizer (manufactured by Coulter). In the present invention, Coulter Multisizer (manufactured by Coulter) is used. Is connected to an interface (manufactured by Nikkaki) for outputting the number distribution and volume distribution and a PC9801 personal computer (manufactured by NEC), and a 1% NaCl aqueous solution is prepared using primary-grade sodium chloride as an electrolytic solution. For example, ISOTON R-II (manufactured by Coulter Scientific Japan) can be used. As a measuring method, 0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant to 100 to 150 ml of the electrolytic aqueous solution, and 2 to 20 mg of a measurement sample (toner) is further added. The electrolyte in which the sample was suspended was subjected to dispersion treatment for about 1 to 3 minutes using an ultrasonic
The volume distribution and the number distribution are calculated by measuring the volume and the number of toner particles of 2 μm or more using the m aperture.

Then, the volume-based weight average particle diameter (D4) obtained from the volume distribution according to the present invention and the number-based length average particle diameter obtained from the volume average particle diameter (D) and the number distribution, ie, The number average particle size (D1) can be determined.

Further, the magnetic toner of the present invention is also preferably characterized in that the magnetic substance is not substantially exposed on the toner surface. Specifically, the magnetic toner present on the surface of the magnetic toner measured by X-ray photoelectron spectroscopy is used. The ratio (B / A) of the iron element content (B) to the carbon element content (A) is 0.00
It is preferably less than 1, and more preferably less than 0.0005. As a result, the magnetic material serving as a charge leak site is not exposed on the surface, and the toner particles can have a high charge amount even under high humidity. For example, even under high humidity, fog is small and transferability is good. Image printing can be performed for a long time, and high image quality and durability stability are remarkably improved. This effect is more remarkable in an image forming method combining a contact transfer step and a cleanerless process.

The method of measuring the ratio (B / A) of the iron element content (B) to the carbon element content (A) present on the toner surface is as follows.

The ratio (B / A) of the iron element content (B) to the carbon element content (A) present on the surface of the toner particles according to the present invention was determined by ESCA (X-ray photoelectron spectroscopy). Calculate by performing composition analysis. In the present invention,
ESCA equipment 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 peak intensity of each element measured.
The surface atomic concentration is calculated using the relative sensitivity factor provided by Company I. In this measurement, the toner was subjected to ultrasonic cleaning, the external additives attached to the surface of the toner particles were removed, and then separated by magnetic force.
It is preferable to dry and measure.

A special toner in which the magnetic particles are not exposed on the surface of the toner particles has already been disclosed in JP-A-7-209904. However, JP-A-7-209904 does not mention the circularity of the disclosed toner. In the image forming method of the present invention, the use of a toner having a specific average circularity is an essential element.
It is unclear whether the same effect is exhibited by using a developer as described in JP-A-2004-204, in a usage form as in the present invention. Further, JP-A-7-209904 does not disclose a dispersion state of a release agent. JP-A-7-209904 describes an example in which polyethylene is used as a toner material. However, if magnetic particles are present at the center of toner particles, polyethylene will be present on the surface of the particles. Exposure from the toner surface is inevitable. as a result,
There is a concern that the physical properties of the toner and the image characteristics may deteriorate.

Further, the toner configuration disclosed in Japanese Patent Application Laid-Open No. 7-209904 can be summarized as follows. From the structure in which a resin layer free of magnetic particles is formed in the vicinity of the toner particle surface with a thickness of a certain amount or more. Consisting of
This means that the toner surface layer portion where no magnetic particles exist is present in a considerable proportion. However, in other words, if the average particle diameter of such a toner is as small as 10 μm, for example, the volume in which the magnetic particles can exist is small, so that it is difficult to include a sufficient amount of the magnetic particles. Moreover, with such toner,
In the particle size distribution of the toner, the ratio of the surface resin layer where no magnetic particles are present differs between the toner particles having a large particle size and the particles having a small particle size. And the selective developability depending on the particle size is easily observed.
Therefore, when printing is performed 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, toner particles having a large particle diameter, are likely to remain, resulting in a decrease in image density and image quality, and further, deterioration in fixability. Also leads to.

As can be seen from the above description, the preferred magnetic substance dispersed state in the toner particles is a state in which the magnetic particles are present in the toner particles as uniformly as possible without agglomeration. Of the magnetic toner related to the image forming method of (1). That is, when the volume average particle diameter of the toner is C and the minimum value of the distance between the magnetic material and the surface of the toner particles is D in the tomographic observation of the magnetic toner using a transmission electron microscope (TEM), D / C ≦ 0.
The use of the magnetic toner No. 02 is also one of the features of the present invention.

In the present invention, the number of toner particles satisfying the relationship of D / C ≦ 0.02 is preferably at least 50%, more preferably at least 65%, even more preferably at least 75%. The reason is as follows.

When D / C ≦ 0.02 is not satisfied,
In the toner particles, no magnetic particles exist at least outside the boundary of D / C = 0.02. Assuming that the above particles are spherical, 1
When one toner particle is defined as the entire space, at least 11.5% of the space where the magnetic substance does not exist is present on the surface of the toner particle. Actually, since the magnetic particles are not uniformly arranged at the closest position so as to form an inner wall inside the toner particles, it is apparent that the magnetic particles become 12% or more. If the magnetic material particles do not exist in such a space per particle, the magnetic material will be biased inside the toner particles, and the possibility of aggregation of the magnetic material will extremely increase. 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 formed 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 particles, fusing or deformation is likely to occur, and handling during the production is difficult. Of the toner, the distribution of the powder characteristics of the toner obtained by the deformation is increased, the electrophotographic characteristics are adversely affected, and the blocking property during storage of the toner is likely to be deteriorated. In the particle structure in which the toner particles have only the binder resin and wax and the magnetic particles are unevenly distributed inside, the exterior of the toner particles is soft and the inside is hard, so that the embedding of the external additive is very likely to occur. The durability of the tire deteriorates. 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 properties and a deterioration in durability tend to be remarkable.

Therefore, in the present invention, the number of toner particles satisfying D / C ≦ 0.02 is preferably 50% or more.

As a specific observation method by TEM,
After sufficiently dispersing the particles to be observed in the room temperature curable epoxy resin, the cured product obtained by curing for 2 days in an atmosphere at a temperature of 40 ° C. is used as it is or frozen by a microtome equipped with diamond teeth. The method of observing as a flaky sample is preferable.

A specific method for determining the ratio of the number of the corresponding particles is as follows.

For the particles for determining D / C by TEM, the equivalent circle diameter was determined from the cross-sectional area in a micrograph, and the value whose value was included in the range of ± 10% of the number average particle size was determined as the corresponding particle. And calculate D / C. The ratio of the particles having a D / C value of 0.02 or less calculated in this way is defined as being determined by the following equation. 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 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.

[0194]

(Equation 9) The number average particle size of the magnetic toner is preferably determined by a Coulter counter described later. <3> Manufacturing method of magnetic toner of the present invention In the case of manufacturing the toner of the present invention by a pulverization method, a known method is used. For example, the above-mentioned binder resin, magnetic substance, release agent, charge control agent In some cases, components necessary as a toner such as a colorant and other additives are sufficiently mixed by a mixer such as a Henschel mixer or a ball mill, and then melt-kneaded using a heat kneader such as a heating roll, a kneader or an extruder. While the resins are mutually compatible with each other, another toner material such as a magnetic substance is further dispersed or dissolved as necessary, and after cooling and solidification, pulverization, classification, and surface treatment as necessary, the toner is processed. The toner of the present invention can be obtained by obtaining particles and, if necessary, adding and mixing an inorganic fine powder. 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 pulverization step can be performed by a method using a known pulverizer such as a mechanical impact type or a jet type.
In order to obtain a toner having a specific degree of circularity according to the present invention, it is preferable to further apply heat to pulverize or supplementally apply a mechanical impact. Also,
A hot-water bath method in which finely pulverized (classified as necessary) toner particles are dispersed in hot water, a method in which the toner particles pass through a hot air flow, 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, Ltd. or a turbo mill manufactured by Turbo Industries, 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 near the glass transition point Tg of the toner (Tg ±
A thermomechanical impact applied at 30 ° C.) is preferable from the viewpoint of preventing aggregation and productivity. More preferably, the temperature is in the range of the glass transition point (Tg ± 20 ° C.) of the toner, which is particularly effective for improving the transfer efficiency.

Furthermore, the toner of the present invention is disclosed in
No. 6,139,945 or the like, a method of atomizing a molten mixture into air using a disk or a multi-fluid nozzle to obtain a spherical toner, or a method using a water-soluble organic solvent which is soluble in a monomer and insoluble in a polymer obtained. The toner can also be produced by a dispersion polymerization method of directly producing a toner or a method of producing a toner using an emulsion polymerization method typified by a soap-free polymerization method of producing a toner by directly polymerizing in the presence of a water-soluble polar polymerization initiator. is there.

The toner according to the present invention can be produced by a pulverization method. However, the toner particles obtained by the pulverization method are generally irregular in shape, and the average particle size, which is an essential component of the toner according to the present invention, is required. In order to obtain a physical property with a circularity of 0.970 or more and a mode circularity of 0.99, it is necessary to perform mechanical / thermal or some special processing. Further, in the pulverization method, since the magnetic substance is essentially exposed on the surface of the toner particles, it is difficult to satisfy the essential toner component requirement of the present invention that the magnetic substance is not substantially exposed on the surface of the magnetic toner. In some cases, the problem of improving image characteristics and durability under high humidity cannot be solved.

Therefore, in order to solve the above-mentioned problems, in the present invention, the toner is preferably produced by a suspension polymerization method. In this suspension polymerization method, a polymerizable monomer, a colorant such as a magnetic substance, and a release agent (and, if necessary, a polymerization initiator, a crosslinking agent, a charge control agent, and other additives) are uniformly dissolved or dissolved. After dispersing into a monomer composition,
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. . In the toner obtained by the suspension polymerization method (hereinafter referred to as “polymerized toner”), since the individual toner particle shapes are substantially spherical, a toner having an average circularity of 0.970 or more and satisfying the physical property requirements of the present invention is required. It is easy to obtain, and furthermore, such a toner has a relatively uniform distribution of the charge amount, and thus has high transferability.

However, even if 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 because the magnetic substance is generally hydrophilic and thus easily exists on the toner surface. The magnetic substance moves randomly when the aqueous solvent is stirred, and the surface of the suspended particles composed of the monomer is dragged by the magnetic substance. It is considered that the shape is distorted and it is difficult to form a circle. In order to solve such a problem, it is necessary to use a magnetic substance having a good dispersion state in a hexane solution as described above, and for that purpose, a coupling agent having a modified surface property of the magnetic substance. It is preferable to use a magnetic material surface-treated with. 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, when the average circularity is 0.970 or more, and the mode circularity is 0.99 or more, the iron element content relative to the carbon element content (A) present on the surface of the magnetic toner measured by X-ray photoelectron spectroscopy analysis Ratio of quantity (B) (B
/ A) is less than 0.001.

To set the number of toner particles satisfying the relationship of D / C ≦ 0.02 to 50% or more, for example,
When the magnetic toner particles are manufactured by the suspension polymerization method, the amount of the resin having a polar functional group for forming the surface layer of the toner particles is adjusted to the polymerizable monomer composition, It can be produced by adjusting the degree of hydrophobicity.

Further, the ratio D4 / D1 of the toner is 1.4.
And the weight average particle diameter of the toner of 3 to 10 μm can be achieved by appropriately selecting the stirring conditions during the polymerization and the dispersion stabilizer to be used. In particular,
When the stirring is increased, the particle size decreases, and when the stirring is reduced, the particle size increases.

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

As the polymerizable monomer constituting the polymerizable monomer system used in the polymerized toner according to the present invention, those described above can be used.

In the production of the polymerized toner according to the present invention, the polymerization may be carried out by adding a resin to the monomer system. 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 that cannot be used because it dissolves in an aqueous suspension to cause emulsion polymerization due to water solubility. When it is desired to introduce a monomer component into the toner, a random copolymer of these and a vinyl compound such as styrene or ethylene, a block copolymer,
Alternatively, it can be used in the form of a copolymer such as a graft copolymer, or in the form of a polycondensate such as polyester or polyamide, or a polyaddition polymer such as polyether or polyimine. When such a high molecular polymer containing a polar functional group is coexisted in the toner, the above-mentioned surface-treated magnetic substance and the wax component are phase-separated, the encapsulation becomes stronger, and the anti-offset properties, anti-blocking properties, and low-temperature fixing properties are improved. Good toner can be obtained. When a polymer having such a polar functional group is used, its average molecular weight is 5,000.
The above is preferably used. 5,000 or less, especially 4,
When the molecular weight is less than 000, 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.

In addition, resins other than those described above may be added to the monomer system for the purpose of improving the dispersibility and fixing property of the material or the image characteristics. Examples of the resin used include polystyrene and polyvinyl toluene. Such as styrene and a substituted styrene; 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,
A polyester resin, a polyamide resin, an epoxy resin, a polyacrylic acid resin, a rosin, a modified rosin, a temper resin, a phenol resin, an aliphatic or alicyclic hydrocarbon resin, an aromatic petroleum resin and the like can be used alone or in combination.

The addition amount of these resins is
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 becomes difficult to design various physical properties of the polymerized toner.

Further, when a polymer having a molecular weight different from the molecular weight range of the 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 in the production of the polymerized toner according to the present invention, one having a half life of 0.5 to 30 hours at the time of the polymerization reaction may be used in an amount of 0.5 to 20 mass% based on the polymerizable monomer. When the polymerization reaction is carried out with the added amount of parts, 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. Examples of the polymerization initiator include 2,2′-azobis-
(2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2′-azobis-4-methoxy-2, Azo or diazo polymerization initiators such as 4-dimethylvaleronitrile and azobisisobutyronitrile, benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide, A peroxide-based polymerization initiator such as lauroyl peroxide may be used.

When producing the polymerized toner according to the present invention, a crosslinking agent may be added, and the preferable addition amount is 0.001 to 15% by weight.

In the method for producing a polymerized toner according to the present invention, generally, the above-mentioned toner composition, that is, a polymerizable monomer, a magnetic substance, a release agent, a plasticizer, a charge control agent, a cross-linking agent, a coloring agent, etc. Components necessary for the toner and other additives, for example, an organic solvent to be added to reduce the viscosity of the polymer formed by the polymerization reaction, a high-molecular polymer, a dispersant and the like are appropriately added, and a homogenizer, a ball mill, a colloid mill, A monomer system uniformly dissolved or dispersed by a disperser such as 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 make the desired toner particle size at once. As for the timing of the addition of the polymerization initiator, it may be added at the same time as the other additives are added to the polymerizable monomer, or may be mixed immediately before being suspended in the 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 the granulation, stirring may be performed using a conventional stirrer to such an extent that the particle state is maintained and the particles are prevented from floating and settling.

In producing the polymerized toner according to the present invention, known surfactants and organic / inorganic dispersants can be used as dispersion stabilizers. Above all, inorganic dispersants are unlikely to produce harmful ultrafine powders, and because of their steric hindrance, they have obtained dispersion stability, so that even if the reaction temperature is changed, their stability is not easily lost, and they are easy to wash and do not adversely affect the toner. Can be preferably used. 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,
Inorganic salts such as barium sulfate; and inorganic oxides such as calcium hydroxide, magnesium hydroxide, aluminum hydroxide, silica, bentonite, and alumina.

[0216] 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 was 40
The polymerization is carried out at a temperature of at least 50 ° C., generally from 50 to 90 ° C. When the polymerization is carried out in this temperature range, the release agent and waxes to be sealed inside are precipitated by phase separation, and the encapsulation becomes more complete. In order to consume the remaining polymerizable monomer, the reaction temperature is 90 to 90 at the end of the polymerization reaction.
It is possible to increase to 150 ° C.

After polymerization is completed, the polymerized toner particles are filtered, washed and dried by a known method, mixed with an inorganic fine powder and adhered to the surface to obtain a toner.
In addition, it is also a desirable embodiment of the present invention to insert a classification step into the manufacturing process and cut coarse or fine powder.

The magnetic toner particles of the present invention include those produced entirely by the suspension polymerization method as described above, but magnetic toner particles partially produced by the suspension polymerization may be used. Examples of toner particles partially manufactured by suspension polymerization include a mixture of a charge control agent and toner particles. This method also enables optimal control of the charge amount according to the developing system, and in the image forming method of the present invention, the balance between the toner particle size distribution and the triboelectric charge amount can be further stabilized. .

The magnetic toner of the present invention not only has good selective developability, but also has little fog and high transferability, so that it is suitable for an image forming method using a contact charging step and further a cleanerless image forming method. Used, and these forms of use are also part of the present invention. In the image forming method including the contact charging step, the key technology is to reduce the toner that is transferred to the charging step without being transferred, that is, the transfer residual toner and the fogging toner. By using toner, the image forming method of the present invention is achieved.

Further, in the cleaner-less image forming method, the transfer residual toner passes through the charging step and is collected in the developing device in the developing step. However, such toner has poor charging properties due to the dispersibility of the material. Since these are many, they are accumulated in the developing device together with the durability, and the image characteristics are easily deteriorated. However, since all the toner particles of the magnetic toner of the present invention have uniformly good image characteristics, even when used in a cleaner-less image forming method at a high temperature, which is easily affected by the dispersion state of the release agent, over a long period of time. Since the high image quality can be stably maintained, the image forming method of the present invention is achieved by using this magnetic toner. <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, the image carrier, and a toner carrier for carrying a magnetic toner on the surface are arranged at a fixed interval, and the magnetic toner is disposed on the toner carrier surface more than the gap. Developing the toner image by transferring the magnetic toner to the electrostatic latent image in a developing unit to which an alternating voltage is applied, and developing the toner image formed on the image carrier. An image forming method comprising at least a transfer step of electrostatically transferring to a transfer material, wherein the toner on the toner carrier in the developing step is the magnetic toner of the present invention.

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 primary charging roller 117 as a contact charging member, a developing device 140, a transfer roller 114, and a cleaner 1 are provided around a photosensitive drum 100 as an image carrier.
16, a register roller 124, and the like. Then, the photosensitive drum 100 is charged to -700 V by the primary charging roller 117. (The applied voltage is AC voltage-2.
0 kVpp (Vpp: peak-to-peak potential), DC voltage -70
0 Vdc) Then, the photosensitive drum 100 is exposed by irradiating the photosensitive drum 100 with a laser beam 123 by the laser beam scanner 121. The electrostatic latent image on the photosensitive drum 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 in contact with the photosensitive drum via the transfer material. The transfer material 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. Further, the toner partially left on the photosensitive drum is cleaned by the cleaner 116. The developing device 140 is provided with a cylindrical toner carrier 102 (hereinafter also referred to as a “developing sleeve”) made of a nonmagnetic metal such as aluminum or stainless steel in the vicinity of the photosensitive drum 100. The gap with the developing sleeve 102 is maintained at about 300 μm by a sleeve / photosensitive drum gap holding member (not shown). This gap is
It is possible to change if necessary. Developing sleeve 10
Although not shown, a magnet roller is fixed and disposed concentrically with the developing sleeve 102 in the inside 2. However,
The developing sleeve 102 is rotatable. The magnet roller has a plurality of magnetic poles, S1 is development, N1 is toner coating amount regulation, S2 is toner take-in / conveyance,
N2 has an effect on preventing toner from blowing out. An elastic blade 103 is provided as a toner layer thickness regulating member that regulates the amount of magnetic toner adhered and conveyed to the developing sleeve 102, and the toner conveyed to the developing area by the contact pressure of the elastic blade 103 against the developing sleeve 102. The amount is controlled. In the developing area, a developing bias of a DC voltage and an AC voltage is applied between the photosensitive drum 100 and the developing sleeve 102, and the toner on the developing sleeve 102 flies on the photosensitive drum 100 in accordance with the electrostatic latent image to form a visible image. Becomes

In the image forming method of the present invention, it is preferable that the charging member is in contact with the image carrier. This is because the absence of ozone is a preferable form of environmental protection.

As a preferable process condition when the charging roller is used as shown in FIG. 1, the charging roller is in contact with the photosensitive drum by forming a contact portion, and the contact pressure on the photosensitive drum is 4.9 to less. 490 N / m (5 to 500 g / c
In m), a DC voltage 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, the AC voltage is 0.5 to 5 kVpp, the AC frequency is 50 to 5 kHz, and the DC voltage is ± 0.2 to ± 5.
kV is preferred.

Although good charging properties can be obtained with only a DC voltage applied to the contact charging member, an AC voltage (alternating voltage) is superimposed on a DC voltage as in the 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 powder between the charging member and the image carrier. It is preferable that the material is electrically conductive because the image carrier is charged by applying the voltage. Therefore, the charging member is
A brush comprising a conductive elastic roller, a conductive elastic blade, a magnetic brush portion magnetically restraining magnetic particles, and a magnetic brush contact charging member or a conductive fiber in which the magnetic brush portion is brought into contact with a photoreceptor; It is preferable and preferable.

Further, a release coating may be provided on those surfaces. Nylon resin, PVdF
(Polyvinylidene fluoride), PVdC (polyvinylidene chloride), fluoroacrylic resin, and the like are applicable.

In the image forming method of the present invention, the developing step includes an image forming simultaneous cleaning step or a cleanerless 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 powder contained therein adheres to the image carrier in the developing step, remains on the image carrier after the transfer step, and is carried and interposed.

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

An appropriate amount of the conductive fine powder contained in the toner is transferred to the electrostatic latent image on the image carrier in the developing step 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 powder on the image carrier also adheres 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 the conductive fine powder on the image carrier is conductive. , 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 untransferred toner remaining on the surface of the image carrier after the transfer and the above-mentioned residual conductive fine powder are transferred to the charging portion 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 image carrier surface, and adheres and mixes into the contact charging member. Therefore, the contact charging of the image carrier is performed in a state where the conductive fine powder is interposed in the contact portion between the image carrier and the contact charging member.

The presence of the conductive fine powder makes it possible to maintain the close contact property and contact resistance of the contact charging member to the image carrier irrespective of contamination due to adhesion and mixing of the transfer residual toner to the contact charging member. Thus, 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 powder contained in the toner moves to the image carrier surface in the developing section, and is carried to the charging section via the transfer section by the movement of the image carrying surface. Since the conductive fine powder is continuously supplied to the charging unit one after another, even if the conductive fine powder is dropped or degraded in the charging unit or deteriorates, it is prevented that the charging property is reduced. Good chargeability is stably maintained.

If the amount of the conductive fine powder in the contact portion between the image carrier and the contact charging member is too small, the lubricating effect of the conductive fine powder cannot be sufficiently obtained, and the contact between the image carrier and the contact charging member is insufficient. The friction with the member is large, and it is difficult to rotate 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 powder may not be obtained, so that sufficient charging performance cannot be obtained. On the other hand, if the intervening amount is too large, the detachment of the conductive fine powder from the contact charging member is remarkably increased, which may adversely affect image formation.

From the above, the amount of the conductive fine powder at the contact portion between the image carrier and the contact charging member is 1 × 10 ^3.
Pcs / mm ² or more, more preferably 1 × 10 ⁴ to
5 × 10 ⁵ pieces / mm ² is good. If it is lower than 1 × 10 ³ / mm ² , a sufficient lubricating effect and an effect of increasing the contact chance cannot be obtained, and the charging performance may be reduced. 1 × 10 ⁴ pieces / mm ²
If the value is lower than the above range, the charging performance may decrease when the amount of the transfer residual toner is large.

The application density range of the conductive fine powder is also determined by what density the conductive fine powder is applied on the image carrier to obtain a 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).

The upper limit of the amount of the conductive fine powder applied is:
This is until the conductive fine powder is evenly applied on one layer on the image carrier, and if it is applied more than that, the effect is not improved. On the contrary, 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 powder, it cannot be said unconditionally. However, if it is to be noted that the conductive fine powder is uniformly formed on the image carrier in one layer. The amount applied is the upper limit.

The amount of the conductive fine powder was 5 × 10 ⁵ pieces / mm ²
If the ratio exceeds the above range, the falling of the conductive fine powder onto the image carrier is remarkably increased, and an insufficient amount of light is exposed on the image carrier regardless of the light transmittance of the fine powder itself. 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 powder 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 ~
An intervening amount of 5 × 10 ⁵ pieces / mm ² is preferred.

A method for measuring the amount of conductive fine powder present in the charging contact portion and the amount of conductive fine powder present on the image carrier in the electrostatic latent image forming step will be described. It is desirable to directly measure the amount of conductive fine powder interposed between the contact charging member and the contact surface of the image carrier, but there is a speed difference between the surface of the contact charging member forming the contact portion and the surface of the image carrier. In this case, most of the powder present on the image carrier before coming into contact with the contact charging member is peeled off by the contacting charging member while moving in the opposite direction. The amount of powder on the surface of the immediately preceding 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 powder is 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 so as 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 a photoreceptor for electrophotography is used as a member to be charged, a volume resistivity of 10 ³ to 10 ⁸ Ω · cm, more preferably 10 ⁴ to 10 ⁷ Ω, in order to obtain sufficient chargeability and leakage resistance.
・ It is good to have a resistance of cm.

As for the volume resistance value of the roller member, 100 V is applied between the core metal and the aluminum drum in a state where 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 rubber or foam medium resistance layer 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%.

The material of the roller member is not limited to an elastic foam. Examples of the material of the elastic material 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.

[0257] Examples of the core metal used for the roller member include aluminum and SUS.

The roller member is disposed so as to be pressed against a charged member as an image bearing member against a resilience with a predetermined pressing force against a resilient member, and a charging contact portion which is a contact portion between the roller member and the image bearing member 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.

As the brush member as the contact charging member, there is a generally used charging brush in which the resistance is adjusted by dispersing a conductive material in fibers. 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 hundred 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 the one used for the charging roller member.

The volume resistance value of the charging brush is 10 ³ to obtain sufficient charging performance and leakage resistance as in the case of the roller member.
The resistance is preferably from 10 to 10 ⁸ Ω · cm.

As the material of the charging brush, conductive rayon fibers REC-B and REC-B manufactured by Unitika Ltd. are 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. 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 moving speed at the contact portion between the contact charging member and the image carrier can be improved. This is preferable in that the opportunity for the conductive fine powder to come into contact with the image carrier is remarkably increased, higher contact properties can be obtained, and direct injection chargeability is improved.

By interposing conductive fine particles in the contact portion between the contact charging member and the image carrier, the lubricating effect (friction reducing effect) of the conductive fine powder causes the contact between the contact charging member and the image carrier. It is possible to provide a speed difference without significantly increasing the torque and remarkably shaving the surface of the contact charging member and 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 structure for providing a speed difference, a speed difference can be provided between the image bearing member and the contact charging member by driving the contact charging member to rotate. The peripheral speed ratio described here can be expressed by the following equation (5) (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).

[0271]

## EQU10 ## Peripheral speed ratio (%) = (charging member peripheral speed / image carrier peripheral speed) × 100 Equation (5) An index indicating the relative speed difference is a relative moving speed represented by the following equation (6). There is a ratio.

[0272]

Relative moving speed ratio (%) = | (Vc−Vp) / Vp | × 100 Equation (6) (where, Vc is the moving speed of the surface of the charging member, and Vp is the moving speed of the surface of the image carrier). Vc is Vc when the charging member surface moves in the same direction as the image carrier surface at the contact portion.
The value has the same sign as p. ) The relative moving speed ratio is usually 10 to 500%.

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

Next, the image carrier will be described. In the image forming method of the present invention, the volume resistance value of the outermost layer of the image carrier (hereinafter, also referred to as “photoconductor”) is 1 × 10 ⁹ or more,
It is preferably less than 1 × 10 ¹⁵ Ω · cm. When the outermost layer of the photoreceptor has a volume resistance value in the above range, more favorable charging properties can be provided, 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 resistance value of the outermost surface layer is preferably less than 1 × 10 ¹⁵ Ω · cm. On the other hand, in order to hold the electrostatic latent image as the image carrier for a certain period of time, the volume resistance value of the outermost layer is 1
It is preferably at least 10 ⁹ Ω · cm.

The method of measuring the volume resistivity of the outermost surface layer of the image carrier according to the present invention is the same as that of the outermost surface layer of the image carrier 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.

The photoreceptor of the present invention comprises amorphous selenium,
It is preferably a photosensitive drum or a photosensitive belt having a photoconductive substance such as amorphous silicon, CdS, ZnO ₂ or an organic photosensitive substance.

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. Examples of the material having the releasability of (3) include one or more kinds of lubricating fine particles selected from a fluorine resin, a silicone resin, a polyolefin resin, and the like. Among them, a compound containing a fluorine atom, that is, polytetrafluoroethylene,
Examples include polyvinylidene fluoride and carbon fluoride.

By these means, the contact angle of water on the surface of the photoreceptor 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, the contact angle with water can be increased by increasing the amount of the lubricating fine particles added to the resin of the surface layer.

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

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

In order to incorporate these lubricating fine particles into the surface of the photoreceptor, a layer in which the lubricating fine particles are dispersed in a resin used for the surface layer is provided on the outermost surface of the photoreceptor, or
As long as the organic photoreceptor is originally composed mainly of resin, it is sufficient to disperse the lubricating fine particles in the outermost surface layer without providing a new surface layer. The amount of addition is preferably 1 to 60% by mass, more preferably 2 to 50% by mass, based on the total weight 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.

The image forming method of the present invention is a direct charging method in which the charging step is such that the charging member is brought into contact with the photosensitive member so as to form a contact portion, and the photosensitive member is charged by applying a voltage. Although it is preferable in that the generation of ozone is small, the load on the photoreceptor surface is larger than that of a method using a corona discharge or the like in which the charging means does not come into contact with the photoreceptor. Remarkable,
This is one of preferred application forms.

One preferred embodiment of the photosensitive member used in the present invention will be described below. The photoreceptor has an organic photosensitive layer on a conductive substrate.

As the organic photosensitive layer, the photosensitive layer may be a single layer type containing the same charge generation substance and charge transport 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.
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 are used. On these conductive substrates, the purpose is to improve the adhesion of the photosensitive layer, improve the coating properties, protect the substrate, cover defects on the substrate, improve the charge injection property from the substrate, and protect the photosensitive layer against electrical breakdown. An undercoating layer may be provided as a base.

The undercoat layer is made of polyvinyl alcohol, poly-N-vinylimidazole, polyethylene oxide, ethyl cellulose, methyl cellulose, nitrocellulose, ethylene-acrylic acid copolymer, polyvinyl butyral, phenolic resin, casein, polyamide, copolymerized nylon, nylon, It is formed of a material such as gelatin, polyurethane, and aluminum oxide. The film pressure is usually 0.1 to 10 μm, preferably about 0.1 to 3 μm.

The charge generation layer is made 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 a charge generating substance such as an inorganic substance such as amorphous silicon in a suitable binder and coating or vapor-depositing. The binder can be selected from a wide range of binder resins, for example, polycarbonate resin, polyester resin, polyvinyl butyral resin, polystyrene resin, acrylic resin, methacryl resin, phenol resin, silicone resin, epoxy resin, vinyl acetate resin, etc. Is mentioned.
The amount of the binder contained in the charge generation layer is selected to be 80% by mass or less, preferably 0 to 40% by mass. The film pressure of the charge generation layer is preferably 5 μm or less, particularly preferably 0.05 to 2 μm.

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 material in a solvent together with a binder as necessary, and applying the solution. The film pressure is generally 5 to 40 μm. As the charge transport substance, a polycyclic aromatic compound having a structure such as biphenylene / anthracene / pyrene / phenanthrene in a main chain or a side chain; a nitrogen-containing cyclic compound such as indole / carbazole / oxadiazole / pyrazoline; a hydrazone compound; Styryl compounds, selenium, selenium-tellurium, amorphous silicon, cadmium sulfide, and the like.

Examples of the binder for dispersing these charge transporting substances include resins such as polycarbonate resin, polyester resin, polymethacrylate ester, polystyrene resin, acrylic resin, polyamide resin, and poly-N-vinylcarbazole / polyvinylanthracene. And the like.

Further, a protective layer may be provided as a surface layer. As the resin for the protective layer, polyester, polycarbonate, acrylic resin, epoxy resin, phenol resin, or a curing agent of these resins alone or
It is used in combination of more than one species.

Further, conductive fine particles may be dispersed in the resin of the protective layer. Examples of the conductive fine particles include metals and metal oxides. Preferably, zinc oxide, titanium oxide, tin oxide, antimony oxide, indium oxide, bismuth oxide, tin oxide coating titanium oxide, tin coating indium oxide. There are ultrafine particles such as antimony-coated tin oxide and zirconium oxide. These may be used alone or as a mixture of two or more.

In general, when particles are dispersed in a protective layer,
In order to prevent scattering of the incident light by the dispersed particles, it is necessary that the particle diameter of the particles is smaller than the wavelength of the incident light, and the conductive fine 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 in the protective layer is preferably from 2 to 90% by mass, and more preferably from 5 to 80% by mass based on the total weight of the protective layer.
Is more preferred. The thickness of the protective layer is preferably from 0.1 to 10 μm, more preferably from 1 to 7 μm.

The surface layer can be applied by spray coating, beam coating or permeation (dipping) coating of the resin dispersion.

Next, the contact transfer step preferably applied in the image forming method of the present invention will be specifically described. In the present invention, the recording medium that receives the transfer of the toner image from the image carrier may be an intermediate transfer member such as a transfer drum. When the recording medium is an intermediate transfer member, a toner image is obtained by transferring the intermediate transfer member to a transfer material such as paper again.

In the contact transfer step, the developed image is electrostatically transferred onto 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, and the conductive elastic layer is made of urethane or EPDM in which a conductive material such as carbon is dispersed, and has a volume resistance of 1 × 10 ⁶ to
It is made of an elastic material of about 1 × 10 ¹⁰ Ω · cm, and a transfer bias is applied by a transfer bias power supply 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 a 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, and examples thereof include those described above.

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 image forming method of the present invention, in order to obtain high image quality without fog, the layer thickness on the toner carrier is smaller than the closest distance between the toner carrier and the photoconductor (between SD). The development is performed in a development step of applying a magnetic toner and applying an AC voltage to perform development. That is, the toner layer thickness regulating member for regulating the magnetic toner on the toner carrier is used so that the closest gap between the photoconductor and the toner carrier is wider than the toner layer thickness on the toner carrier. The toner layer thickness regulating member that regulates the magnetic toner on the carrier is regulated by the elastic member that is in contact with the toner carrier via the toner, so that the toner is hardly affected by the temperature and humidity environment, and the toner scatters. This is particularly preferable from the viewpoint of obtaining a uniform charge that is unlikely to occur.

In the present invention, it is preferable that the toner carrier is disposed so as to face the photosensitive member with a distance of 100 to 1000 μm. If the separation distance of the toner carrier from the photoconductor is smaller than 100 μm, the change in the developing characteristic of the toner with respect to the fluctuation of the separation distance becomes large, so that it is difficult to mass-produce an image forming apparatus satisfying stable image quality. Sometimes. If the separation distance of the toner carrier from the photoconductor is greater than 1000 μm, the ability of the toner to follow the latent image on the photoconductor is reduced, resulting in degradation of image quality such as resolution and image density. Preferably, the thickness is 120 to 500 μm.

In the present invention, 5 to 5
Preferably, a toner layer of 0 g / m ² is formed, and the toner is transferred from the toner layer to a photoreceptor to develop an electrostatic latent image. If the amount of toner on the toner carrier is less than 5 g / m ^2, it is difficult to obtain a sufficient image density, and the toner layer becomes uneven due to excessive charging of the toner. If the amount of toner on the toner carrier is more than 50 g / m ² , toner scattering is likely to occur.

In the present invention, the toner is preferably developed in a developing step in which an alternating electric field is applied to the toner carrier to perform the development. The applied developing bias may be such that the alternating voltage (AC voltage) is superimposed on the DC voltage. Good.

As the waveform of the AC voltage used for the developing bias, 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 1 × 10 ⁶ to 1 × 10 ⁷ V / m and a frequency of 100 to 500 are provided between the toner carrier and the image carrier for carrying the toner.
It is preferable to apply an alternating electric field of 0 Hz as a developing bias.

As the toner carrier used in the present invention, a conductive cylinder (developing roller) formed of a metal or alloy such as aluminum or stainless steel is preferably used. Further, the conductive cylinder may be formed of a resin composition having sufficient mechanical strength and conductivity, or a conductive rubber roller may be used. Further, the present invention is not limited to the cylindrical shape as described above, and may be in the form of an endless belt that is driven to rotate.

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

If Ra is less than 0.2 μm, the charge amount on the toner carrier increases, and the developability becomes insufficient. When Ra exceeds 3.5 μm, unevenness occurs in the toner coat layer on the toner carrier, resulting in uneven image density. 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 measured 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 is extracted from the roughness curve in the direction of the center line as the measurement length a,
The center line of the extracted portion is the X axis, and the direction of the vertical magnification is Y.
When the axis and the roughness curve are represented by y = f (x), the following equation (7) is obtained.
Is expressed in micrometer (μm).

[0311]

(Equation 12) Further, since the magnetic toner of the present invention has a high charging ability, it is desirable to control the total charge amount of the toner during development, and the surface of the toner carrier according to the present invention has conductive fine particles and / or lubricant dispersed therein. It is preferable that the resin layer is covered with a resin layer.

In the coating layer of the toner carrier, the conductive fine particles contained in the resin material were 11.7 MPa (120 kPa).
g / cm ² ), and preferably has a resistance value of 0.5 Ω · cm or less after being pressed.

The conductive fine particles used for the toner carrier are preferably carbon fine particles, a mixture of carbon fine particles and crystalline graphite, or crystalline graphite. The conductive fine particles preferably have a particle size of 0.005 to 10 μm.

Examples of the resin material include thermoplastic resins such as styrene resins, vinyl resins, polyether sulfone resins, polycarbonate resins, polyphenylene oxide resins, polyamide resins, fluororesins, cellulose resins, and acrylic resins; A thermosetting resin such as a resin, a polyester resin, an alkyd resin, a phenol resin, a melamine resin, a polyurethane resin, a urea resin, a silicone resin, and a polyimide resin or a photocurable resin can be used.

Among them, those having a releasable property such as silicone resin and fluorine resin, or polyether sulfone,
Polycarbonate, polyphenylene oxide, polyamide, phenolic resin, polyester, polyurethane,
Those having excellent mechanical properties such as styrene resins are more preferable. Particularly, a phenol resin is preferable.

The conductive fine particles used for the toner carrier are preferably used in an amount of 3 to 20 parts by mass per 10 parts by mass of the resin component of the coating layer.

In the case where carbon fine particles and graphite particles are used in combination, it is preferable to use 1 to 50 parts by mass of carbon fine particles per 10 parts by mass of graphite.

The volume resistivity of the resin coating layer of the toner carrier in which the conductive fine particles are dispersed is from 1 × 10 ⁻⁶ to 1 × 10 ^6.
Ω · cm is preferred.

In the present invention, the surface of the toner carrier that carries 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. When the moving directions are the same, it is desirable that the ratio is at least 100% with respect to the moving speed of the image carrier.
If it is less than 100%, the image quality is poor. The higher the moving speed ratio, the larger the amount of toner supplied to the development site, the more frequently the toner is attached to and detached from the latent image, and unnecessary portions are scraped off and added to necessary portions repeatedly. As a result, an image faithful to the latent image can be obtained. Specifically, the moving speed of the surface of the toner carrier is preferably 1.05 to 3.0 times the moving speed of the surface of the image carrier. <5> Process Cartridge of the Present Invention The process cartridge of the present invention is configured to be detachable from the image forming apparatus used in the image forming method of the present invention, and is at least selected from the group consisting of an image carrier and a charging unit. One means is supported integrally with the developing means.

The developing means used in the process cartridge of the present invention includes a normal developing device having a toner, a toner container for storing the toner, a toner carrier, and the like.

It is preferable to use the above-described magnetic toner of the present invention as the toner used in the process cartridge of the present invention.

Since the developing means is a detachable process cartridge as described above, even if the life of the toner has expired, the image forming apparatus can be realized only by changing each means and member. It can be used without waste.

[0323]

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.

[0324] All parts in the following formulations are parts by mass.

The method for measuring the toner and other physical properties of the present invention can be measured by the methods described in the above detailed description. <1> Production of Magnetic Body Surface-treated magnetic bodies 1 to 8 and magnetic body 1 were obtained as follows. <Production of surface-treated 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.

While maintaining the pH of the aqueous solution at around 9, empty
Air to oxidize at 80-90 ° C
This gave a slurry of the particles. After washing and filtering,
The Lee's solution was once removed. At this time, a small amount of the water-containing sample
Sampled and measured for water content. Next, this wet sump
Re-dispersed in another aqueous medium without drying.
Adjust the pH of the dispersion to about 6 and stir well
Pulling agent (n-C _TenH_{twenty one}Si (OCH_Three)_Three) Magnetic
0.2 parts by mass with respect to iron oxide (The amount of magnetic particles is
(Calculated as the water content minus the water content).
A pulling process was performed. Use the generated hydrophobic magnetic material in the usual way
Further washing, filtration and drying, the obtained particles are sufficiently crushed
did. Next, 0.3 parts by mass based on the obtained hydrophobic magnetic material.
Silane coupling agent (n-C_TenH_{twenty one}Si (OC
H_Three)_Three) Dry-hydrophobic treatment again and surface treatment
Magnetic substance 1 was obtained. Table 1 shows the physical properties of the obtained surface-treated magnetic material.
Shown in <Production of magnetic body 1> As in the production of surface-treated magnetic body 1,
Reaction, the magnetic iron oxide particles generated after the oxidation reaction
After washing, filtering and drying, the aggregated particles are crushed
Magnetic substance 1 was obtained. <Production of surface-treated magnetic substance 2>
After redispersion in the medium, adjust the pH of the redispersion solution to about 6.
Silane coupling agent (n-C_Ten
H_{twenty one}Si (OCH_Three)_Three) For the surface-treated magnetic material 1
5 parts by mass were added to perform a coupling treatment. Got
The magnetic particle slurry is washed, filtered and dried in a usual manner, and
The particles that have been aggregated are crushed and surface-treated
2 was obtained. Table 1 shows the physical properties of the obtained surface-treated magnetic material 2.
You. <Production of surface-treated magnetic substance 3> For production of surface-treated magnetic substance 2
Silane coupling agent (n-C_TenH_{twenty one}Si (O
CH_Three)_Three) Is 0.5 parts by mass with respect to the magnetic material 1
Manufacture of surface-treated magnetic material 2 except for surface treatment in gas phase
In the same manner as in the above, a surface-treated magnetic material 3 was obtained. Obtained magnetism
Table 1 shows the physical properties of the body. <Production of surface-treated magnetic material 4> As silane coupling agent
And (n-C_TenH_{twenty one}Si (OCH_Three)_Three) Instead of (n-
C₆H₁₃Si (OCH_Three)_ThreeSurface treated magnet except using)
The surface-treated magnetic material 4 is formed by the same method as that for manufacturing the sexual material 1.
Obtained. Table 1 shows the physical properties of the obtained magnetic material. <Production of surface-treated magnetic material 5> As silane coupling agent
And (n-C_TenH_{twenty one}Si (OCH_Three)_Three) Instead of (n-
C₁₈H₃₇Si (OCH_Three)_ThreeSurface treated magnet except using)
The surface-treated magnetic material 5 is formed by the same method as that for manufacturing the sexual material 1.
Obtained. Table 1 shows the physical properties of the obtained magnetic material. <Production of surface-treated magnetic materials 6 to 8> Production of surface-treated magnetic materials 1
Manufacturing conditions (pH, stirring speed, oxidation
Reaction rate, air blowing amount, etc.) and the amount of hydrophobizing agent
The surface-treated magnetic materials 6 to 8 were obtained with appropriate changes. The resulting magnet
Table 1 shows the physical properties of the sex bodies.

[0327]

[Table 1] <2> Production of conductive fine powder Conductive fine powders 1 to 5 were obtained as follows. <Conductive Fine Powder 1> Fine particle zinc oxide having a volume average particle diameter of 3.7 μm, 6.6 volume% of 0.5 μm or less in particle size distribution and 8 number% of 5 μm or more (resistance: 80 Ω · cm, primary particle diameter: 0.1 μm). A product obtained by granulating primary zinc oxide particles of 1 to 0.3 μm under pressure (white) is referred to as conductive fine powder 1.

This conductive fine powder 1 was observed under 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 light wavelength 7 of a laser beam scanner used for image exposure in the image forming apparatus of the first embodiment described later.
Using a light source with a wavelength of 740 nm according to 40 nm,
The transmittance in this wavelength range is determined by X-Rite 310T.
When measured using a transmission densitometer, the transmittance of the conductive fine powder 1 was about 35%. <Conductive fine powder 2> A volume average particle diameter of 2.4 μm and a particle size distribution of 0.4 μm obtained by classifying the conductive fine powder 1 by wind power.
Fine zinc oxide (resistance: 440 Ω · cm, transmittance: 35%) in which 5 μm or less is 4.1 volume% and 5 μm or more is 1 number% is defined as the conductive fine powder 2.

Observation of this conductive fine powder 2 with a scanning electron microscope revealed that it was composed of primary particles of zinc oxide of 0.1 to 0.3 μm and aggregates of 1 to 5 μm. Compared with 1, the primary particles were reduced. <Conductive Fine Powder 3> A volume average particle size of 1.5 μm, obtained by classifying the conductive fine powder 1 by air classification, and a particle size distribution of 0.1 μm.
The conductive fine powder 3 is made of fine zinc oxide (resistance 1500 Ω · cm, transmittance 35%) having a volume of 5% or less of 35% by volume and a size of 5 μm or more of 0% by number. Observation of the conductive fine powder 3 with a scanning electron microscope revealed that the conductive fine powder 3 was composed of 0.1 to 0.3 μm zinc oxide primary particles and 1 to 4 μm aggregates. Then, the primary particles increased. <Conductive fine powder 4> The volume average particle diameter is 0.3 μm, and 80 μm is 0.5% or less in the particle size distribution and 0 is 5 μm or more
Number% of fine particle zinc oxide (resistance: 100 Ω · cm, primary particle diameter: 0.1 to 0.3 μm, white, transmittance: 35%, purity: 9)
9% or more) as the conductive fine powder 4. Observation of this conductive fine powder 4 with a scanning electron microscope revealed that it was composed of 0.1-0.3 μm zinc oxide primary particles with few aggregates. <Conductive Fine Powder 5> Aluminum borate having a volume average particle size of 2.8 μm, surface-treated with tin oxide / antimony, is subjected to air classification to remove coarse particles, and then repeatedly dispersed in an aqueous system and filtered. Excluding fine particles, the volume average particle size was 3.2 μm,
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 powder 5.

The following Table 2 shows the typical physical property values of the conductive fine powders 1 to 5.

[0332]

[Table 2] <3> Production of Magnetic Toner (a) Production of Magnetic Toner Particles <Production of Magnetic Toner Particles> 451 g of a 0.1 M Na ₃ PO ₄ aqueous solution was charged into 709 g of ion-exchanged water and heated to 60 ° C. After slowly adding 67.7 g of a 0.0M CaCl ₂ aqueous solution, hydrochloric acid was added to adjust the pH of the solution to about 8.5.
To obtain an aqueous medium containing Ca ₃ (PO ₄ ) ₂ .・ Styrene 80 parts ・ n-butyl acrylate 20 parts ・ Unsaturated polyester resin 5 parts ・ Negative charge control agent (monoazo dye-based Fe compound) (compound represented by the following general formula (III)) 1 part ・ Surface treatment magnetism 90 parts of body 1

[0333]

Embedded image The above formulation was uniformly dispersed and mixed using an attritor (Mitsui Miike Kakoki Co., Ltd.). The negative charge control agent used in the following magnetic toner is also represented by the above general formula (III).

This monomer composition was heated to 60 ° C., and 20 parts of an ester wax mainly composed of behenyl behenate (maximum endothermic peak in DSC: 72 ° C.) was added and mixed, and polymerization was started. 2,2'-azobis (2,4-dimethylvaleronitrile) [t1 / 2 = 140
Min, at 60 ° C.] and 2 g of dimethyl-2,2′-azobisisobutyrate [t1 / 2 = 270 minutes, 60 ° C .; t1 / 2 = 80 minutes, 80 ° C.] were dissolved. .

The above-mentioned polymerizable monomer system was charged into the above-mentioned aqueous medium, and a TK homomixer (Tokusai Kika Kogyo Co., Ltd.) at 10,000 rpm at 60 ° C. under an N ₂ atmosphere.
The mixture was stirred for 5 minutes and granulated. Thereafter, the mixture was reacted at 60 ° C. for 7 hours while stirring with a paddle stirring blade. After that, the liquid temperature was 80 ° C.
Then, stirring was further continued for 3 hours. After completion of the reaction, the suspension was cooled, hydrochloric acid was added to dissolve Ca ₃ (PO ₄ ) ₂ , and filtration was performed.
After washing with water and drying, magnetic toner particles 1 having a weight average particle size of 6.6 μm were obtained.

Table 3 shows the physical properties of the obtained magnetic toner particles 1 together with those of the magnetic toner particles obtained in the following production of the magnetic toner particles. <Production of Magnetic Toner Particles 2 to 8> In the production of the magnetic toner particles 1, the magnetic toner particles 2 to 8 were respectively produced in the same manner except that the surface-treated magnetic substances 2 to 8 were used instead of the surface-treated magnetic substance 1. Obtained. <Production of Magnetic Toner Particles 9> Magnetic toner particles 9 were obtained in the same manner as in the production of magnetic toner particles 1 except that the magnetic material 1 was used instead of the surface-treated magnetic material 1. <Production of Magnetic Toner Particles 10> In the production of the magnetic toner particles 1, Ca ₃ (PO ₄ ) ₂ in the aqueous medium was adjusted by adjusting the amount of the aqueous Na ₃ PO ₄ solution and the amount of the CaCl ₂ aqueous solution added.
By changing the amount and further using sodium dodecylbenzenesulfonate, magnetic toner particles 10 having a weight average particle size of 2.9 μm were obtained. <Production of magnetic toner particles 11 and 12> Magnetic toner particles 1
In the production of, the prescription amount of the surface-treated magnetic material 1 was 9 parts,
Magnetic toner particles 11 and 12 were obtained in the same manner except that the amount was changed to 02 parts. <Production of magnetic toner particles 13 and 14> Magnetic toner particles 1
In the preparation of
And toner toner particles 13 and 14 were obtained in the same manner except that the amount was changed to 50.6 parts. <Production of Magnetic Toner Particles 15> In the production of magnetic toner particles 1, a wax mainly composed of polyethene instead of ester wax (maximum endothermic peak 1 in DSC).
15 ° C.) to obtain magnetic toner particles 15 in the same manner. <Production of Magnetic Toner Particles 16> 451 g of a 0.1 M Na ₃ PO ₄ aqueous solution was added to 709 g of ion-exchanged water, heated to 60 ° C., and 67.7 g of a 1.0 M CaCl ₂ aqueous solution was gradually added. , Hydrochloric acid was added to adjust the pH of the solution to about 8.5.
To obtain an aqueous medium containing Ca ₃ (PO ₄ ) ₂ .・ Styrene 80 parts ・ n-butyl acrylate 20 parts ・ Unsaturated polyester resin 5 parts ・ Negative charge control agent (monoazo dye-based Fe compound) 1.2 parts ・ Surface treated magnetic material 1 108 parts Attritor The mixture was uniformly dispersed and mixed using Mitsui Miike Kakoki Co., Ltd.). This monomer composition was heated to 60 ° C., and 24 parts of the ester wax used in the production of the magnetic toner particles 1 was added thereto and mixed, and the polymerization initiator 2,2′-azobis (2,4- Dimethylvaleronitrile) [t1 / 2 = 140 minutes, at 60 DEG C.] 7.2 parts and dimethyl-2,2'-azobisisobutyrate [t1 / 2
= 270 minutes, at 60 ° C; t1 / 2 = 80 minutes, at 80 ° C].

The above-mentioned polymerizable monomer system was charged into the above-mentioned aqueous medium, and a TK homomixer (Tokusai Kika Kogyo Co., Ltd.) was used at 10,000 rpm at 60 ° C. in an N ₂ atmosphere.
The mixture was stirred for 5 minutes and granulated. Thereafter, the mixture was reacted at 60 ° C. for 3 hours while stirring with a paddle stirring blade. After that, the liquid temperature was 80 ° C.
The stirring was further continued for 1 hour. Next, in this aqueous suspension, 16 parts of styrene, 4 parts of n-butyl acrylate, 0.4 part of 2,2′-azobis (2,4-dimethylvaleronitrile) 0.4 part of sodium behenate 0.1 part A mixture of 20 parts of water was added, and the mixture was again kept at 80 ° C. for 6 hours with stirring. After completion of the reaction, the suspension was cooled, hydrochloric acid was added to dissolve Ca ₃ (PO ₄ ) ₂ , and the resultant was filtered, washed with water and dried to obtain magnetic toner particles 16 having a weight average particle diameter of 7.5 μm. <Production of Magnetic Toner Particles 17>-100 parts of styrene / n-butyl acrylate copolymer (weight ratio 80/20)-5 parts of unsaturated polyester resin-1 part of negative charge control agent (monoazo dye-based Fe compound) -90 parts of surface-treated magnetic material-10 parts of ester wax used in the production of magnetic toner particles 1 The above materials were mixed by a blender, melted and kneaded by a twin-screw extruder heated to 110 ° C, and the cooled kneaded material was mixed. After coarsely pulverizing with a hammer mill, the coarsely pulverized product was finely pulverized with a turbo mill (manufactured by Turbo Kogyo Co., Ltd.), and the obtained finely pulverized product was subjected to air classification to obtain black powder 17 having a weight average particle size of 7.5 μm. <Production of Magnetic Toner Particles 18>
Was subjected to spheroidization using an impact type surface treatment apparatus (processing temperature: 55 ° C., rotational processing blade peripheral speed: 90 m / sec.) To obtain magnetic toner particles 18.

[0338]

[Table 3] (B) Production of Magnetic Toner <Production of Magnetic Toner 1> 100 parts of magnetic toner particles 1 were treated with hexamethyldisilazane on silica having a number average primary particle diameter of 12 nm, then treated with silicone oil, and BET after the treatment was performed. Magnetic toner 1 was prepared by mixing 1 part of hydrophobic silica fine powder having a value of 140 m ² / g with a Henschel mixer (Mitsui Miike Kakoki Co., Ltd.).

The formulation of the magnetic toner 1 is shown in the following Production Examples of Magnetic Toners 2 to 21 and Comparative Magnetic Toners 1 ′ to 1 ′.
The results are shown in Table 4 together with those of 5 ′. <Production of Magnetic Toner 2> Magnetic toner 2 was prepared by mixing 100 parts of magnetic toner particles 2 with 0.6 part of the hydrophobic silica fine powder used in the production of magnetic toner 1. <Production of Magnetic Toners 3 to 6>
The magnetic toners 3 to 6 were prepared by mixing 1 part of the hydrophobic silica fine powder used in the production of the magnetic toner 1 with 00 parts. <Production of Magnetic Toners 7 and 8> Magnetic toners 7 and 8 were prepared by mixing 100 parts of magnetic toner particles 8 and 12 with 0.6 part of the hydrophobic silica fine powder used in the production of magnetic toner 1. did. <Production of magnetic toners 9 and 10> Magnetic toner particles 13 and 1
4 and 100 parts of the hydrophobic silica fine powder used in the production of the magnetic toner 1 were mixed with 100 parts to prepare magnetic toners 9 and 10. <Production of magnetic toner 11>
The magnetic toner 11 was prepared by mixing 0.6 parts of the hydrophobic silica fine powder used in the production of the magnetic toner 1 with the parts. <Production of magnetic toner 12>
Then, 1 part of the hydrophobic silica fine powder used in the production of the magnetic toner 1 was mixed with 1 part of the toner to prepare a magnetic toner 12. <Production of magnetic toner 13>
The magnetic toner 13 was prepared by mixing 1.0 part of the hydrophobic silica fine powder used in the production of the magnetic toner 1 with the parts. <Production of Magnetic Toners 14 to 16>
To 00 parts, 1 part of hydrophobic silica fine powder having a BET value of 200 m ² / g after treating the surface with hexamethyldisilazane, and treating the surface with iso-butyltrimethoxysilane, 1 part of 100 m ² / g hydrophobic titanium oxide fine powder or 1 part of hydrophobic alumina fine powder having a BET value of 150 m ² / g after treating the surface with iso-butyltrimethoxysilane, Magnetic toner 14-
16 were prepared. <Production of Magnetic Toner 17> One part of the hydrophobic silica fine powder used in the production of the magnetic toner 1 and 2 parts of the conductive fine powder 1 were mixed with 100 parts of the magnetic toner particles 1 to prepare the magnetic toner 17. Prepared. <Production of Magnetic Toners 18 to 21>
The magnetic toners 18 to 21 were prepared by mixing 1 part of the hydrophobic silica fine powder used in the production of the magnetic toner 1 and 2 parts of each of the conductive fine powders 2 to 5 with respect to 00 parts. <Production of Magnetic Toner 1 ′> Magnetic toner 1 ′ was prepared by mixing 100 parts of magnetic toner particles 3 with 0.6 part of the hydrophobic silica fine powder used in the production of magnetic toner 1. <Production of Magnetic Toner 2 ′> A magnetic toner 2 ′ was prepared by mixing 100 parts of the magnetic toner particles 9 with 0.6 part of the hydrophobic silica fine powder used in the production of the magnetic toner 1. <Production of Magnetic Toner 3 ′>
The toner was mixed with 2.0 parts of the hydrophobic silica fine powder used in the production of the magnetic toner 1 to prepare a magnetic toner 3 ′. <Production of Magnetic Toner 4 ′>
Then, 0.6 parts of the hydrophobic silica fine powder used in the production of the magnetic toner 1 was mixed with the above parts to prepare a magnetic toner 4 ′. <Production of Magnetic Toner 5 ′>
To 1.0 part of the hydrophobic toner fine powder used in the production of the magnetic toner 1 was mixed with the resulting toner to prepare a magnetic toner 5 ′.

[0340]

[Table 4]

[0341]

Example 1 As an image forming apparatus, LBP-1760 was modified and used as shown in FIG. 1 similar to that shown in the above embodiment.

First, the following photosensitive member 1 was manufactured as an image bearing member used in Examples of the present invention. <Production of Photoreceptor 1> An aluminum cylinder having a diameter of 30 mm was used as a base for the photoreceptor. Then, layers having the configuration shown in FIG. 3 were sequentially laminated by dip coating to form a photoreceptor 1. (1) Conductive coating layer: mainly composed of tin oxide and titanium oxide powder dispersed in a phenol resin. 15μ thickness
m. (2) Undercoat layer: mainly composed of modified nylon and copolymerized nylon. The film thickness is 0.6 μm. (3) Charge generation layer: mainly composed of an azo pigment having absorption in a long wavelength region dispersed in butyral resin. Thickness 0.6
μm. (4) Charge transport layer: 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 a polytetrafluoroethylene powder ( (Average particle size: 0.2 μm) was added at 10% by mass based on the total solid content, and the mixture was uniformly dispersed. 25 μm thick. The contact angle with water is 95
Degree.

The measurement of the contact angle was performed using pure water, and the apparatus used was a contact angle meter CA-X, manufactured by Kyowa Interface Science Co., Ltd. The organic photoconductor (OPC) drum of the photoconductor 1 obtained above was used as an image carrier. A rubber roller charger coated with nylon resin and dispersed with conductive carbon as a primary charging member is brought into contact with the photoreceptor (contact pressure 60 g / c).
m), DC voltage -700 Vdc and AC voltage 2.0 kVp
A bias on which p is superimposed is applied to uniformly charge the photosensitive member. Following the primary charging, an electrostatic latent image is formed by exposing the image portion with a laser beam. At this time, the dark portion potential V
d = −700 V and the light portion potential VL = −150 V.

The gap between the photosensitive drum and the developing sleeve is 30
0 μm, and a layer thickness of about 7
Using a developing sleeve in which a resin layer having a thickness of 1.0 μm and a JIS center line average roughness (Ra) of 1.0 μm is formed on a 16 mm diameter aluminum cylinder whose surface is blasted, a developing magnetic pole 85
mT (850 gauss), thickness 1.
A silicone rubber blade having a length of 0 mm and a free length of 1.0 mm was contacted with a linear pressure of 29.4 N / m (30 g / cm). -100 parts of phenolic resin-90 parts of graphite (average particle size: about 7 m)-10 parts of carbon black Next, a DC bias voltage of -500 V superimposed with an AC voltage having a frequency of 2000 Hz and a peak-to-peak voltage of 1600 V was used as a developing bias. Further, the peripheral speed of the developing sleeve is 11
The speed was set to 0% (103 mm / sec).

Further, as shown in FIG. 4, a transfer roller (made of ethylene-propylene rubber in which conductive carbon is dispersed, the volume resistivity of the conductive elastic layer is 10 ⁸ Ω · cm, and the surface rubber hardness is 24
゜, diameter 20 mm, contact pressure 59 N / m (60 g / c
m)) is changed to the peripheral speed of the photoconductor in the direction A in FIG. 4 (94 mm / sec).
c) at a constant speed, and the transfer bias is DC 1.5 kV
And

As a fixing method, an LBP-1760 fixing device which does not have an oil application function and uses heat and pressure fixing by a heater via a film was used. 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 is 180
° C and the nip width were set to 7 mm.

First, the magnetic toner 1 was used as the magnetic toner. First, it was left at a temperature of 50 ° C. for 3 days. Thereafter, an image forming test was performed with the magnetic toner at 30 ° C. and 80% RH. 90g / m for transfer material
² paper was used. As a result, the magnetic toner 1 showed a high transferability at the initial stage, no missing characters or lines during the transfer, and a good image without fog on the non-image portion was obtained.

Next, durability was evaluated using an image pattern having a printing ratio of 4%.

The image evaluation was performed as follows.

The transfer efficiency was determined by tapping the transfer residual toner on the photoreceptor after the transfer of the solid black image with a Mylar tape, peeling it off, and applying the Macbeth density value on the paper to c,
Assuming that the Macbeth density of the Mylar tape pasted on the paper on which the toner before transfer and the toner is fixed is d and the Macbeth density of the Mylar tape pasted on the unused paper is e, approximately the following equation (8) is used. Calculated.

[0351]

(Equation 13) If the transfer efficiency is 90% or more, there is no problem in the image.

The resolving power in the early stage of durability was evaluated by the reproducibility of a small-diameter isolated dot at 600 dpi, in which the electric field is easily closed by the latent image electric field and is difficult to reproduce. ◎ Very good: 5 or less defects in 100 ○ Good: 6 to 10 defects in 100 △ Practical: 11 to 20 defects in 100 × Not practical: Defect in 100 Is 20 or more Fog measurement of non-image part is made by Tokyo Denshoku REFL
Measured using ECTMETER MODEL TC-6DS. A green filter was used as a filter, and it was calculated from the following equation (9). The smaller the value, the less fog.

[0353]

Fog (reflectance) (%) = reflectance (%) on standard paper−reflectance (%) of sample non-image portion Equation (9) If fog is 2.0% or less, a good image is obtained. It is. The image density was measured with a Macbeth densitometer RD918 (manufactured by Macbeth). The initial image density was the density of the 20th image output. The fixing offset property was determined by observing the stains generated on the back side of the image sample from the initial stage to 100 sheets of durability, and counting the number of sheets generated.

The state of dispersion of the release agent inside the toner particles was determined by evaluating image characteristics and durability after being left at 50 ° C. for 3 days. When the dispersion state of the release agent is not good, a part of the release agent is exposed on the toner surface by this standing, and the toner performance is deteriorated. Table 5 shows the obtained results.
Shown in As can be seen from Table 5, the magnetic toner 1 was at 50 ° C.
In the evaluation of durability after standing for 3 days, good results were obtained up to 2000 sheets of printing.

[0355]

Examples 2 to 21 Magnetic toners 2 to 2 were used.
Using No. 21, an image-drawing test and durability evaluation were performed under the same conditions as in Example 1. As a result, no problem was found in the initial image characteristics, and no significant problem was obtained up to 2000 prints. Table 5 shows the results.

[0356]

Comparative Examples 1 to 5 Magnetic toners 1 'to
Using 5 ′, an image formation test and durability evaluation were performed by the same image forming method as in Example 1. As a result, there was a problem in the image characteristics immediately after standing, and the image quality worsened with the durability test. This is considered to reflect the uneven dispersion state of the release agent inside the toner particles. Table 5 shows the results.

[0357]

[Table 5]

[0358]

Embodiment 22 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.

First, the following photosensitive member 2 was manufactured as an image bearing member used in Examples of the present invention. <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 structure shown in FIG. 6 were sequentially laminated by dip coating to prepare a photoreceptor. (1) Conductive layer: A conductive particle-dispersed resin layer (tin oxide and titanium oxide) having a thickness of about 20 μm provided to smooth defects of an aluminum cylinder and to prevent the occurrence of moire due to the reflection of laser exposure. Of which are mainly dispersed in a phenol resin). (2) a positive charge injection prevention layer (subbing layer): serves the positive charge injected from the aluminum substrate are prevented from canceling the negative charge on the photoreceptor surface, ¹⁰⁶ by methoxymethylated nylon This is a medium resistance layer having a thickness of about 1 μm and a resistance adjusted to about Ω · cm. (3) Charge generation layer: a layer having a thickness of about 0.3 μm in which a disazo pigment is dispersed in a butyral resin, and which generates positive and negative charge pairs when subjected to laser exposure. (4) 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) Charge injection layer: A layer obtained by dispersing conductive tin oxide ultrafine particles and ethylene tetrafluoride resin particles having a particle size of about 0.25 μm in a photocurable acrylic resin. More specifically, the particle diameter is reduced to about 0.03 μm by doping with antimony.
100% by mass of the tin oxide particles with respect to the resin, 20% by mass of polytetrafluoroethylene resin particles, and 1.
2% by mass dispersed. 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 surface resistance of the obtained photosensitive member was 5 × 10
¹² Ω · cm, the contact angle of water on the photoreceptor surface is 102
°.

Next, a production example of 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 had a resistance of 10 ⁵ Ω · cm and a hardness of 30 degrees in Asker C hardness. Also,
Observation of the surface of the charging roller with a scanning electron microscope revealed that the average cell diameter was about 90 μm and the porosity was 55%.

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

The image forming apparatus of this embodiment is a laser printer (recording apparatus) of a simultaneous cleaning process (cleanerless system) using a transfer type electrophotographic process.
It is. It has a process cartridge from which a cleaning unit having a cleaning member such as a cleaning blade has been removed, and uses a magnetic toner as a developer,
This is an example of non-contact development in which a toner layer on a toner carrier and an image carrier are arranged in non-contact. (1) Overall Schematic Configuration of the Printer of the Example The rotating drum type OPC photoconductor 21 of the photoconductor 2 obtained above as an image carrier is 94 mm / s in the X direction of the arrow.
It is rotationally driven at a peripheral speed of ec (process speed).

The charging roller 22, which is the charging member 1 as a contact charging member, is disposed so as to be pressed against the photosensitive member 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 this example, the charging roller 22 is rotationally driven at a peripheral speed of 100% in a facing direction (a direction opposite to the moving direction of the surface of the photoconductor = direction of arrow Y) at a charging contact portion n which is a contact surface with the photoconductor 21. ing. That is, the charging roller 22 as a contact charging member
Has a speed difference with respect to the surface of the photoreceptor 21.
Further, the amount of application is approximately 1 × on the surface of the charging roller 22.
Conductive fine powder 1 so as to be uniform at 10 ⁴ pieces / mm ²
Was applied.

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 embodiment, the surface of the photoconductor 21 is uniformly charged by a 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) 2 including a laser diode, a polygon mirror and the like as exposure means
Numeral 3 outputs a laser beam intensity-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 21 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.

The electrostatic latent image on the surface of the photoreceptor 21 is developed by the developing device 24 as a toner image.

The developing device 24 of this embodiment is a non-contact type reversal developing device using the magnetic toner 17 used in Embodiment 17 as a developer. As described above, the conductive fine powder 1 is externally added to the magnetic toner 17.

The gap between the photosensitive drum 21 and the developing sleeve 24a as a toner carrier is 310 μm, and the developing sleeve 24a has a layer thickness of about 7 μm having the following structure, according to JIS.
Using a developing sleeve in which a resin layer having a center line average roughness (Ra) of 1.0 μm is formed on an aluminum cylinder having a diameter of 16 mm whose surface is blasted, a developing magnetic pole of 90 mT (900
Gauss) magnet roll, and a urethane elastic blade 24c having a thickness of 1.0 mm and a free length of 1.5 mm as a toner layer thickness regulating member is 29.4 N / m (30 g / m2).
cm). • 100 parts of phenolic resin • 90 parts of graphite (average particle size of about 7 μm) • 10 parts of carbon black Further, in the developing section a (developing area section) facing the photoconductor 21, the order of the rotation of the photoconductor 21 is changed. Direction (arrow W direction)
Then, the photosensitive member 21 is rotated at a peripheral speed of 120% of the peripheral speed.

The developing sleeve 24a has an elastic blade 2
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 toner coated on a was 16 g / m ² .

[0371] 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 sleeve 24a.

Further, a developing bias voltage is applied to the developing sleeve 24a from a developing bias applying power source. The developing bias voltage is a DC voltage of -420 V and a frequency of 1600.
Hz, peak-to-peak voltage 1500 V (electric field strength 5 × 10 ⁶ V
/ M), and one-component jumping development was performed between the developing sleeve 24a and the photosensitive member 21a using a superimposed rectangular AC voltage.

The transfer roller 25 having a medium resistance as a contact transfer means is pressed against the photosensitive member 21 with a linear pressure of 98 N / m (100 g / cm) to form a transfer nip portion 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, and a predetermined transfer bias voltage is applied to a transfer roller 25 from a transfer bias application power supply. Then, 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 roller resistance value is 5 × 10 ⁸ Ω · c
m, and transfer was performed by applying a DC voltage of +3000 V. 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 electrostatically pressed and pressed. Is transcribed.

Reference numeral 26 denotes a fixing device such as a heat fixing method. The transfer material P fed to the transfer nip portion b and receiving the transfer of the toner image on the photoconductor 21 is separated from the surface of the photoconductor 21 and introduced into the fixing device 26, where the toner image is fixed and the image is formed. It is discharged out of the apparatus as a formed product (print, copy).

In the printer of this embodiment, the cleaning unit is removed, and the transfer residual toner remaining on the surface of the photoconductor 21 after the transfer of the toner image onto the transfer material P is not removed by the cleaner, and the rotation of the photoconductor 21 is stopped. Accordingly, the developer reaches the developing section a via the charging contact section n, and is simultaneously cleaned (collected) by the developing device 24.

In the printer of this embodiment, the three process devices of the photoreceptor 21, the charging roller 22, and the developing device 24 are collectively constituted as an image forming apparatus and a process cartridge 27 which are detachably mountable to the printer main body. 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 detachable guide / holding member for the process cartridge. (2) Behavior of the conductive fine powder in the present embodiment The conductive fine powder mixed into the magnetic toner in the developing device 24 is used together with the toner when the developing device 24 develops the toner of the electrostatic latent image on the photoconductor 21 side. An appropriate amount moves to the photoconductor 21 side.

The toner image on the photosensitive member 21 is transferred to the transfer nip b
The transfer material P, which is a recording medium,
However, since the conductive fine powder on the photoconductor 21 is conductive, it does not actively transfer to the transfer material P side, and is substantially transferred onto the photoconductor 21. Adhered and retained.

In the present invention, since the image forming apparatus has no cleaning step, the transfer residual toner remaining on the surface of the photoreceptor 21 after the transfer and the above-mentioned residual conductive fine powder are in contact with the photoreceptor 21 and the contact charging member. Is carried by the movement of the surface of the photoreceptor 21 as it is, and adheres to or mixes with the charging roller 22.
Therefore, direct injection charging of the photoconductor 21 is performed in a state where the conductive fine powder is present in the charging contact portion n between the photoconductor 21 and the charging roller 22.

Due to the presence of the conductive fine powder, even if toner adheres to or mixes with the charging roller 22, the charging roller 22 can maintain close contact and contact resistance with the photosensitive member 21. And direct charging of the photoreceptor 21 can be performed.

That is, the charging roller 22 comes into close contact with the photoconductor 21 via the conductive fine powder, and the conductive fine powder present on the mutual contact surface between the charging roller 22 and the photoconductor 21 cleans the surface of the photoconductor 21. By rubbing without gaps, the charging of the photoreceptor 21 by the charging roller 22 becomes stable and safe by direct injection charging without using a discharge phenomenon due to the presence of the conductive fine powder, and can be obtained by conventional roller charging or the like. Thus, a high charging efficiency can be 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 to or mixed into the charging roller 22 is gradually discharged from the charging roller 22 onto the photosensitive member 21, moves to the surface of the photosensitive member 21 and reaches the developing section, and is subjected to simultaneous cleaning (collection) by the developing means. ) Is done.

In the simultaneous development cleaning, the toner remaining on the photoreceptor 21 after the transfer is developed in the subsequent image forming step, that is, the photoreceptor is charged and exposed to form a latent image, and the latent image is developed. In some cases, the fogging bias of the developing device, that is, the fog removing potential difference Vback, which is the potential difference between the DC voltage applied to the developing device and the surface potential of the photosensitive member.
Is to be recovered. In the case of the reversal development as in the printer 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 photoconductor to the developing sleeve by the developing bias and the toner from the developing sleeve to the bright portion potential of the photoconductor. Is caused by the action of an electric field that causes

Also, by operating the image forming apparatus,
The conductive fine powder mixed into the toner of the developing device 24 moves to the surface of the photoreceptor 21 in the developing section a, and is carried to the charging contact section n via the transfer nip section b by the movement of the image bearing surface. Since new particles are continuously supplied to the charging contact part n, even if the conductive fine powder is dropped or the like is reduced in the charging contact part n or the particles are deteriorated, the charging property is reduced. Is prevented from occurring, and good chargeability is stably 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 low in contamination regardless of 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, since the conductive fine powder does not impair the chargeability, the electric resistance is 1 × 10 ^9.
Ω · cm or less. Therefore, when a contact developing device in which the toner directly contacts the photoconductor 21 in the developing unit a is used, the conductive fine powder in the toner passes through
Electric charges are injected into the photosensitive member 21 by the developing bias, and image fogging occurs.

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 have a high potential difference between the two, and the conductive fine powder is easily developed uniformly. High chargeability can be obtained, and a good image can be obtained.

The conductive fine powder is interposed in the charging contact portion n between the charging roller 22 and the photoreceptor 21, so that the charging roller 2 has a lubricating effect (friction reducing effect) of the conductive fine powder.
It is possible to easily and effectively provide a speed difference between the photoconductor 21 and the photoconductor 21.

By providing a speed difference between the charging roller 22 and the photosensitive member 21, the chance that the conductive fine powder contacts the photosensitive member 21 at the charging contact portion n between the charging roller 22 and the photosensitive member 21 is markedly increased. In addition, high contact property can be obtained, and good direct injection charging can be achieved.

In the present embodiment, the charging roller 22 is driven to rotate, and the rotation direction is rotated in the direction opposite to the moving direction of the surface of the photosensitive member 21, so that the charging roller 22 is carried to the charging contact portion n. The transfer residual toner on the photoreceptor 21 is charged by the charging roller 2
2 has the effect of temporarily collecting and leveling. That is, it is possible to perform the direct injection charging by dominating the transfer residual toner on the photoreceptor 21 by the reverse rotation once and performing the charging.

Further, in this embodiment, an appropriate amount of conductive fine powder is interposed in the charging contact portion n between the photosensitive drum 21 as an image carrier and the charging roller 22 as a contact charging member, so that the fine powder is used. Charge roller 22 due to lubrication effect
It is easy to reduce the friction between the photosensitive drum 21 and the photosensitive drum 21 and to rotate the charging roller 22 to rotate the photosensitive drum 21 with a speed difference. That is, the driving torque is reduced, and the surfaces of the charging roller 22 and the photosensitive drum 21 can be prevented from being scraped or damaged. Further, sufficient charging performance can be obtained by increasing the contact chance by the particles. Also, there is no adverse effect on image formation due to the conductive fine powder falling off the charging roller 22. (3) Evaluation In the present embodiment, three toners were stored in the toner cartridge at 50 ° C.
200 g of magnetic toner 17 left for 30 days
An image-drawing test was performed under an environment of 80 ° C. and 80% RH. As the photoconductor, the volume resistance of the outermost surface layer of the photoconductor 2 is 5 × 10
^{Using a 12} Ω · cm photoreceptor, the transfer material is 90 g / m
² paper was used. In the initial image characteristics, no fog due to poor charging was observed, and a good image density with high resolution was obtained. At this time, the photoconductor potential after the direct injection charging was -670 V with respect to the applied charging bias of -690 V. Next, durability was evaluated with an image pattern having a printing ratio of 4%. As a result, image defects due to poor charging did not occur until after 2000 intermittent printing, and good direct injection chargeability was obtained. The photoconductor potential after direct injection charging after 2,000 sheets of intermittent printing is the applied charging bias minus 690.
It was -655 V with respect to V, and the decrease in chargeability from the initial stage was as small as 15 V. No decrease in image quality due to the decrease in chargeability was observed. Table 6 shows the obtained results.
As can be seen from Table 6, when the magnetic toner 17 was used, even in the cleanerless image forming method of the present invention, the selective developing property was small, and the durability was good up to 2,000 sheets.

[0392]

Examples 23 to 26 Durability was evaluated using magnetic toners 18 to 21 under the same conditions as in Example 22. Table 6 shows the obtained results. As can be seen from Table 6, in all of the cleanerless image forming methods, the selective developability was small, and the durability was good up to 2,000 sheets.

[0393]

[Table 6]

[0394]

According to the present invention, a fine magnetic material having a special physical property and an improved dispersibility is contained, and the release material is contained. The magnetic toner having the surface shape and particle size maintains good toner performance even when left in a harsh environment, and can provide high-definition images stably for a long time even when used in a harsh environment. it can.

Further, an image forming method comprising a contact charging method and a magnetic one-component developing method using the magnetic toner of the present invention,
Also, in the image forming apparatus of the contact charging method, the contact transfer method, and the toner recycling process, since the performance of the toner is not deteriorated, it is necessary to stably obtain a good image for a long period of time after repeated use after being left under a severe environment. Can be.

Further, it is possible to use a simple member as the contact charging member, and it is possible to provide a uniform charging property, and to have a simple configuration, no obstacle due to an ozone product, an obstacle due to poor charging, and a low cost. It is possible to obtain a simple image forming apparatus and a process cartridge.

[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 charging characteristic graph of a contact charging member.

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 22 to 26.

FIG. 6 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: photosensitive drum (image carrier) 102: developing sleeve (toner carrier) 103: elastic blade 114: transfer roller 116: cleaner 117: primary charging roller 121: laser beam scanner 124: register roller 125: transport belt 126: Fixing device 140: developing device 141: stirring member P: transfer material 34: transfer roller 34a: core metal 34b: conductive elastic layer 21: photoconductor 22: charging roller 22a: core metal 23: laser beam scanner 24: developing device 24a : Developing sleeve 24b: stirring member 24c: elastic blade (toner 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 14: 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 9/08 374 G03G 15/02 101 9/087 102 15/02 101 15/06 101 102 15/08 504A 15/06 101 506A 15/08 504 9/08 301 506 101 507 384 15/08 507B (72) Inventor Akira Hashimoto Canon Inc. 3- 30-2 Shimomaruko, Ota-ku, Tokyo (72) Inventor Kawamoto Keiji 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Michihisa Magome 3-30-2 Shimomaruko 3-chome, Ota-ku, Tokyo Inside Canon Inc. 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 2H003 AA18 BB11 CC04 CC05 CC06 2H005 AA02 AA03 AA06 AA08 AA15 AB06 CA14 CB03 CB07 CB13 EA01 EA02 EA03 EA05 EA10 2H068 AA05 AA06 AA08 BB03 BB31 BB33 CA37 CA60 FA27 2H073 BA03 BA06 BA13 CA03 2H077 AA37 AD13 AD17 AD31 AD36 BA07 EA03 EA16 GA02

Claims (49)

[Claims] 1. A magnetic toner having an inorganic fine powder on the surface of magnetic toner particles containing at least a binder resin, a release agent and a magnetic substance, wherein the magnetic toner has an average circularity of 0.970 or more; The weight average particle diameter (D4) is 3 to 10 μm, the magnetic toner particles contain magnetic iron oxide as the magnetic substance, and the magnetic toner has a magnetization in a magnetic field of 79.6 kA / m (1000 Oersted). Has a strength of 10 to 50 Am ² /
kg (emu / g), wherein the magnetic substance is dispersed in a hexane solution,
The absorbance at 500 nm after 5 minutes from the dispersion was a
-5. A magnetic toner, wherein a-5 and a-30 satisfy the following formula (1), where a-30 represents the absorbance at 500 nm after 30 minutes from the dispersion. 0.8 <a-30 / a-5 Equation (1) 2. The magnetic substance, in a dispersed state in a hexane solution, has an absorbance a-5 at 500 nm after 5 minutes from the dispersion and 500 after 60 minutes from the dispersion.
When the absorbance at nm is a-60, a-5, a-
2. The magnetic toner according to claim 1, wherein 60 satisfies the following expression (2). 0.8 <a-60 / a-5 Equation (2) 3. The magnetic material according to claim 1, wherein the magnetic material has a light absorption constant at 500 nm of 1000 or more after 30 minutes from the dispersion in a dispersion state in a hexane solution. toner. 4. The magnetic material according to claim 1, wherein, in a dispersion state in a hexane solution, the extinction constant at 500 nm after 60 minutes from the dispersion is 1000 or more. Item 6. The magnetic toner according to item 1. 5. The volume average particle diameter of the magnetic material is 0.05
The magnetic toner according to any one of claims 1 to 4, wherein the thickness of the magnetic toner is from 0.3 to 0.3 m. 6. The magnetic toner according to claim 1, wherein the magnetic material is surface-treated with a coupling agent in an aqueous medium. 7. The ratio (B / A) of the iron element content (B) to the carbon element content (A) present on the surface of the magnetic toner particles as measured by X-ray photoelectron spectroscopy.
Is less than 0.001.
7. The magnetic toner according to any one of 6. 8. A volume average particle diameter of the magnetic toner is C, and a minimum distance between the magnetic material and the surface of the magnetic toner particles is observed in a tomographic plane observation of the magnetic toner using a transmission electron microscope (TEM). When the value is D, D / C ≦
The magnetic toner according to any one of claims 1 to 7, wherein the number of toner particles satisfying a relationship of 0.02 is 50% or more. 9. The magnetic toner according to claim 1, wherein the number of toner particles satisfying the relationship of D / C ≦ 0.02 is 65% or more. 10. The magnetic toner according to claim 1, wherein the number of toner particles satisfying the relationship of D / C ≦ 0.02 is 75% or more. 11. The magnetic toner according to claim 1, wherein the magnetic toner contains 0.1 to 4% by mass of an inorganic fine powder having a number average primary particle size of 4 to 80 nm. Magnetic toner. 12. The inorganic fine powder is at least one selected from silica, titania, and alumina,
The magnetic toner according to claim 1, wherein the inorganic fine powder has been subjected to a hydrophobic treatment. 13. The magnetic toner according to claim 1, wherein the inorganic fine powder has been subjected to a hydrophobic treatment with at least silicone oil. 14. The magnetic toner according to claim 1, wherein the inorganic fine powder has been subjected to a hydrophobic treatment with at least a silane compound and silicone oil. 15. The magnetic toner according to claim 1, wherein the inorganic fine powder and a conductive fine powder having a volume average particle diameter smaller than a volume average particle diameter of the magnetic toner are provided on the surface of the magnetic toner. 15. The magnetic toner according to any one of 1 to 14. 16. The resistance of the conductive fine powder is 1 × 10
The magnetic toner according to claim 15, wherein the magnetic toner has a resistivity of ⁹ Ω · cm or less. 17. The resistance of the conductive fine powder is 1 × 10
The magnetic toner according to claim 15, wherein the magnetic toner has a resistivity of ⁶ Ω · cm or less. 18. The magnetic toner according to claim 14, wherein the conductive fine powder is non-magnetic. 19. The magnetic toner according to claim 1, wherein the magnetic toner contains 10 to 200 parts by mass of a magnetic substance with respect to 100 parts by mass of a binder resin. 20. The magnetic toner according to claim 1, wherein the magnetic toner particles are partially or entirely manufactured by a suspension polymerization method. 21. The magnetic toner according to claim 1, wherein the magnetic toner contains 0.5 to 50 parts by mass of a release agent based on 100 parts by mass of the binder resin. Magnetic toner. 22. The release agent component has a DSC curve measured by a differential scanning calorimeter of 40 to 1 upon heating.
The magnetic toner according to any one of claims 1 to 21, having a maximum endothermic peak in a region at 10 ° C. 23. The release agent component shows a DSC curve measured by a differential scanning calorimeter of 45 to 9 when the temperature is raised.
The magnetic toner according to any one of claims 1 to 21, having a maximum endothermic peak in a region at 0 ° C. 24. The mode circularity of the magnetic toner is 0.5.
The ratio D4 / D1 between the weight average particle diameter (D4) and the number average particle diameter (D1) is 99 or more, and the ratio D4 / D1 is less than 1.4. Magnetic toner. 25. A charging step of applying a voltage to a 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 the image carrier And a toner carrier for supporting the magnetic toner on the surface are arranged at a fixed interval, and the magnetic toner is coated on the surface of the toner carrier to a thickness smaller than the interval, and an AC voltage is applied. A developing step of developing the toner image by transferring the magnetic toner to the electrostatic latent image in the developing unit, and a transfer step of electrostatically transferring the toner image formed on the image carrier to a transfer material. In the image forming method having at least: the toner on the toner carrier in the developing step is a magnetic toner having an inorganic fine powder on the surface of magnetic toner particles having at least a binder resin, a release agent, and a magnetic material; The toner has an average circularity of 0.970 or more, a weight average particle diameter (D4) of 3 to 10 μm, and the magnetic toner particles contain magnetic iron oxide as the magnetic material. Indicates that the magnetization intensity in a magnetic field of 79.6 kA / m (1000 Oe) is 10 to 50 Am ² /
kg (emu / g), wherein the magnetic substance is dispersed in a hexane solution,
The absorbance at 500 nm after 5 minutes from the dispersion was a
-5. A magnetic toner, wherein a-5 and a-30 satisfy the following formula (1), where a-30 represents the absorbance at 500 nm after 30 minutes from the dispersion. 0.8 <a-30 / a-5 Equation (1) 26. The image forming method according to claim 25, wherein the toner on the toner carrier in the developing step is the magnetic toner according to any one of claims 2 to 24. 27. The method according to claim 2, wherein the developing step also serves as a cleaning step of collecting toner remaining on the image carrier after transferring the toner image onto the transfer material.
27. The image forming method according to 5 or 26. 28. In the charging step, the charging member is in contact with the image carrier by forming a contact portion, and at least a contact portion between the charging member and the image carrier and / or the vicinity thereof is electrically conductive. 25. A fine powder is interposed therebetween.
28. The image forming method according to 27. 29. The charging step is a step of charging the image carrier in a state in which 1 × 10 ³ / mm ² or more conductive fine powders are interposed in a contact portion between the charging member and the image carrier. The image forming method according to claim 28, wherein: 30. 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. 30. The image forming method according to claim 28, wherein: 31. The image forming method according to claim 30, 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. 32. 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 32. The image forming method according to any one of Items 25 to 31. 33. 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
The image forming method according to any one of claims 25 to 32, wherein the content is 5 to 90%. 34. The image forming apparatus according to claim 25, wherein the charging step is a step of charging the image carrier by applying a voltage to a conductive brush-shaped brush member as the charging member. The image forming method according to any one of the above. 35. In the charging step, a DC voltage or a voltage obtained by superimposing an AC voltage having a peak voltage of less than 2 × Vth (Vth: discharge start voltage in DC application) (V) on the DC member is applied to the charging member. 26. The method according to claim 25, wherein the step of charging the image carrier is performed by performing
35. The image forming method according to any one of the items 34. 36. 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 25 to 34, wherein: 37. The image forming apparatus according to claim 25, wherein the outermost layer of the image carrier has a volume resistance of 1 × 10 ⁹ Ω · cm or more and less than 1 × 10 ¹⁵ Ω · cm. The image forming method according to claim 1. 38. The image forming apparatus according to claim 25, 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. 39. A contact angle of the image carrier with water is as follows:
The image forming method according to claim 25, wherein the angle is 85 ° or more. 40. The outermost surface layer of the image bearing member is a resin layer in which at least one or more lubricating fine particles selected from a fluororesin, a silicone resin and a polyolefin resin are dispersed. ~ 39
The image forming method according to any one of the above. 41. The image forming method according to claim 25, wherein the image carrier is a photoconductor using a photoconductive substance. 42. The method according to claim 25, wherein in the electrostatic latent image forming step, image information is written as an electrostatic latent image on a charged surface of the image carrier by image exposure. Image forming method. 43. The image forming method according to claim 25, wherein a gap between the image carrier and the toner carrier in the developing step is 100 to 1000 μm. 44. In the developing step, a toner layer having a thickness smaller than a gap between the image carrier and the toner carrier is formed on the toner carrier, and toner is transferred from the toner layer to the electrostatic latent of the image carrier. The image forming method according to any one of claims 25 to 43, further comprising a step of developing the toner image by transferring the image to an image. 45. The method according to claim 25, wherein in the developing step, the amount of 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 developing step comprises the steps of:
Forming a toner layer to 50 g / m ^2, in any one of claims 25 to 45, characterized in that the step of developing the electrostatic latent image by transferring the toner from the toner layer on the image bearing member The image forming method as described in the above. 47. The developing step is a step of developing an electrostatic latent image on the image carrier by applying at least an alternating electric field as a developing bias between the toner carrier carrying the toner and the image carrier. The alternating electric field has a peak-to-peak electric field intensity of 1 × 10 ⁶ to 1 × 10 ⁷ V / m and a frequency of 100 to 100 V.
47. The frequency is 5000 Hz.
The image forming method according to any one of the above. 48. The transfer step, wherein the transfer member is in contact with an image carrier via a transfer material at the time of transfer, and the toner image on the image bearing member is transferred to the transfer material. The image forming method according to any one of claims 25 to 47. 49. An image carrier for carrying an electrostatic latent image, charging means for applying a voltage to a charging member to charge the image carrier, and an electrostatic latent image on the charged image carrier. An electrostatic latent image forming means for forming an image; and transferring a magnetic 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. The image forming apparatus includes a developing unit, a transfer unit that electrostatically transfers the toner image formed on the surface of the image carrier to a transfer material, and a fixing unit that fixes the toner image on the transfer material. A toner cartridge carried on the toner carrier, wherein at least one unit selected from the group consisting of the image carrier and the charging unit is supported integrally with the developing unit. Is claim 1
23. A process cartridge comprising the toner according to claim 22.