JP2002202627A - Image forming method and magnetic toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide magnetic toners which are less environmentally affected, have stable electrostatic performance, are free of fogging, provide high image density in long-term use, have excellent image reproducibility and fixability and make it possible to obtain good images not giving rise to an electrostatic charge defect in spite of long-term repetitive use and to provide an image forming method which makes it possible to obtain the good images even when using toner particles of a smaller grain size in order to enhance definition. SOLUTION: The following magnetic toners are used in the image forming method of a contact electrostatic charge type. The toners have at least the toner particles containing a binder resin, wax and magnetic powder, inorganic powder and fine conductive powder having the average grain size smaller than the average grain size of the toner particles, the toners have avenge circularity of >=0.960, the magnetic powder is not substantially exposed on the surfaces of the toner particles, the wax contains at least two kinds; the wax soluble in a monomer which is the constitution element of the binder resin and the insoluble wax.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming method for visualizing an electrostatic latent image and a magnetic toner used in the image forming method.

[0002]

2. Description of the Related Art Conventionally, many proposals have been made regarding magnetic toners and image forming methods. U.S. Pat. No. 3,909,258 proposes a method of developing using a magnetic toner having electrical conductivity.
In this technique, a conductive magnetic toner is supported on a cylindrical conductive sleeve having magnetism therein, and is brought into contact with an electrostatic image for development. At this time, in the developing unit, a conductive path is formed by the toner particles between the surface of the recording medium and the surface of the sleeve, and electric charges are guided to the toner particles from the sleeve via the conductive path. The toner particles adhere to the image area by the Coulomb force and are developed.

[0003] This developing method using a conductive magnetic toner is an excellent method which avoids the problems associated with the conventional two-component developing method. However, since the toner is conductive, the developed image can be easily transferred from a recording medium. There is a problem that it is difficult to transfer electrostatically to a final supporting member such as paper.

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

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

Further, a jumping developing method has been proposed in Japanese Patent Application Laid-Open No. 55-18656. This involves applying a very thin layer of magnetic toner on a sleeve, triboelectrically charging it, and then developing it in close proximity to the electrostatic image. This method is an excellent method in that the magnetic toner is applied thinly on the sleeve to increase the chance of contact between the sleeve and the toner, thereby enabling sufficient triboelectric charging.

However, the developing method using the insulating magnetic toner has an unstable factor related to the insulating magnetic toner to be used. The reason for this is that a considerable amount of fine powdered magnetic material is mixed and dispersed in the insulating magnetic toner, and a part of the magnetic material is exposed on the surface of the toner particles. This causes variations or deterioration of various characteristics required for the magnetic toner, such as development characteristics and durability, of the magnetic toner.

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

Hitherto, proposals regarding magnetic iron oxide contained in magnetic toners have been made, but they still have points to be improved. For example, JP-A-62-279352 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 that the shape of magnetic iron oxide is controlled 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 Patent Application Laid-Open No. 61-34070 proposes a method for producing ferric oxide by adding a hydrosilosilicate solution during the oxidation reaction to ferric oxide. Although triiron tetroxide according to this method has a Si element near the surface, the Si element exists in a layer near the surface of the triiron tetroxide, and the surface is vulnerable to mechanical shock such as friction. Have a point.

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

In the pulverization method, it is difficult to completely and uniformly disperse solid fine particles such as a magnetic powder or a colorant in a resin, and depending on the degree of the dispersion, an increase in fog and a decrease in image density may occur. Cause. In addition, the grinding method
In essence, the magnetic iron oxide particles are exposed on the surface of the toner, so that there remains a problem in the fluidity of the toner and the charging stability in a severe environment. That is, in the pulverization method, there is a limit to the fineness of the toner required for high definition and high image quality, and along with this, the powder characteristics, particularly the uniform charging property and fluidity of the toner are remarkably attenuated.

Further, from the viewpoint of ensuring fluidity and transferability, for example, Japanese Patent Application Laid-Open No. 63-235953 discloses a toner which has been made spherical by a mechanical impact force. In order to completely sphericalize the finely divided toner, a considerable amount of energy is required, which increases the cost.In addition, the resulting toner may have a magnetic material or wax in the toner due to thermal shock or the like in the sphering process. It easily appeared on the surface, and was insufficient in terms of securing high image quality and transferability.

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. A toner obtained by suspension polymerization (hereinafter referred to as “polymerized toner”) can be easily formed into fine particles of a toner, and since the obtained toner has a spherical shape, the toner has excellent fluidity, which is advantageous for high image quality.

However, when a magnetic material is contained in the polymerized toner, its fluidity and charging characteristics are significantly reduced. This is because the magnetic particles are generally hydrophilic and thus easily exist on the toner surface. To solve this problem, it is important to modify the surface characteristics of the magnetic material.

Many proposals have been made regarding surface modification for improving the dispersibility of a magnetic substance in a polymerized toner. For example, JP-A-59-200254 and JP-A-59-20025
No. 0256, JP-A-59-200257,
JP-A-59-224102 and the like have proposed various techniques for treating a magnetic substance with a silane coupling agent.
JP-A-3-250660 and JP-A-10-239897 disclose a technique of treating silicon element-containing magnetic particles with a silane coupling agent.

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

As for printer devices, LED and LBP printers have become the mainstream in the recent market, and the direction of technology has been increased to higher resolution, that is, from 240,300 dpi to 400,600,800 dpi. ing. Accordingly, higher definition has been required for the developing system. In addition, the functions of the copying machine have been advanced, and the digital copying machine is moving toward digitalization.

In this direction, since a method of forming an electrostatic charge image by a laser is mainly used, the direction is also moving toward a high resolution direction. Here, similarly to a printer, a high-resolution and high-definition developing method is required, and Japanese Patent Application Laid-Open Nos. 1-112253 and 2-284158 propose toners having a small particle size. However, the various problems described above have not been sufficiently solved. Further, there is a demand for a higher process speed as well as higher resolution and higher definition.

However, it has been found that spherical toners which are advantageous for high image quality and transferability have some problems in fixing. That is, it has been found that one of the problems is that gloss unevenness is likely to occur in a fixed image, and another problem is that low-temperature offset is likely to occur when the heating temperature is relatively low, such as when the apparatus is started. .

With respect to such a phenomenon, a fixing structure with a small fixing pressure, for example, JP-A-63-313182, JP-A-2-157778, and JP-A-4-440.
No. 75, JP-A-4-204980, and the like.
In the induction heating fixing device and the like in which a current is induced in the fixing roller by the magnetic flux described in JP-A-9739 and heat is generated by Joule heat, the spherical toner is relatively denser than the conventional non-spherical toner. The toner tends to clog, so it is easily affected by the pressure of the fixing member.As a result, it is easy to reproduce the "su" of the transfer paper on the image, and the solid image is relatively uneven and offset compared to the non-spherical toner. We think that it tends to occur.

In addition, since the internal / external structure of the toner, such as a capsule structure as disclosed in JP-A-5-088409, can be controlled in the polymerization method toner in which a spherical toner is easily obtained, the softening point of the outer layer resin is compared. It has the advantage that it is easy to achieve both high durability and low-temperature fixability of the toner by means such as setting the softening point of the inner layer resin low, but in order to promote low-temperature fixability, the toner surface layer is substantially It has also been found that when a resin having a high softening point is used, the above-mentioned tendency of fixing unevenness and offset becomes stronger.

In order to perform high-speed fixing, it is indispensable to further secure low-temperature fixing property. However, from the viewpoint of achieving a balance between fixing property and image characteristics, various techniques relating to various release agents have been disclosed. ing.

For the internal addition of wax, for example, JP-A-52-3304, JP-A-52-3305,
Japanese Patent Application Laid-Open No. 57-52574 discloses a technique. These waxes are used for improving the fixing performance of the toner, particularly, the offset resistance. However, while these performances are improved, blocking resistance is deteriorated, and a problem occurs in matching with the image forming means, which impairs developability and the like.

Further, there is disclosed a technique in which two or more kinds of waxes are added to a toner from a low temperature range to a high temperature range at the time of fixing in order to exert the effect of further adding the wax. For example, Japanese Patent Publication No. 52-3305 discloses a combination of polypropylene wax or polyethylene wax and paraffin wax.
No. 59 discloses two kinds of polyalkylene waxes having different melting points and melting points of the respective waxes, and JP-A-4-124676 discloses a polyalkylene wax having a specific molecular weight and a melt viscosity, molecular weight, Combinations of polyethylene waxes with specified acid values and the like are disclosed in
JP-A-334920 discloses a combination of waxes each having a sharp melting peak.
No. 35 discloses a technique such as a combination of two kinds of waxes having different melt viscosities.

However, none of these toners can satisfy all the toner performances, and some problems have occurred. For example, there are disadvantages such as excellent high-temperature offset resistance and developability but poor low-temperature fixability, excellent low-temperature offset resistance but poor blocking resistance, and further causing a decrease in developability. In addition, when a plurality of wax components are used, the dispersion in the toner becomes non-uniform, which causes poor charging of the toner, poor conveyance on the developing device or the developing sleeve, and uneven coating, and causes fog or blotch on the image. Image defects occurred.

Further, the wax is often unevenly distributed in the toner. Particularly, in a high temperature and high humidity environment, an alternating electric field is applied to the toner carrier to reciprocate the toner between the toner carrier and the image carrier. In the developing step of performing development by flying motion, the wax exudes due to the impact with the image carrier many times, and toner fusion is likely to occur. Further, when applied to an image forming method using development and cleaning, toner is likely to fuse due to wax oozing due to rubbing of the image carrier and the charging member.
Such defects also occurred.

Particularly, in the case of a toner obtained by a pulverization method, the effect of the wax composition on the productivity of the toner cannot be ignored. For example, when a wax having a relatively low melting point is used, since the binder resin is plasticized, the mechanical strength of the toner decreases and the pulverization efficiency increases, but the amount of fine powder having a desired particle size or less increases. It falls into a so-called over-pulverized state, the yield at the time of classification decreases, and as a result, the production efficiency deteriorates. On the other hand, when a wax having a relatively high melting point is used, the pulverization efficiency deteriorates, and the dispersibility becomes difficult when melt-kneading the toner. If the kneading state is strengthened to improve the dispersibility, new problems such as molecular breakage of the binder resin occur.

As described above, among the demands for higher image quality and high-speed fixing, there is room for studying toners that satisfy all of them.

On the other hand, as a toner for developing a latent image, a two-component developer composed of a carrier and a toner and a one-component toner (magnetic toner and non-magnetic toner) that does not require a carrier are known. . In the two-component system, the toner is charged mainly by the friction between the carrier and the toner, and in the one-component system, the toner is charged mainly by the friction between the toner and the charging member. Regarding the toner, a method has been proposed in which inorganic fine particles are added as an external additive to toner particles for the purpose of improving the flow characteristics and charging characteristics of the toner and the toner irrespective of the difference between the two-component system and the one-component system. , Widely used.

For example, inorganic fine particles which have been subjected to a hydrophobizing treatment as disclosed in JP-A-5-66608 and JP-A-4-9860 or inorganic fine particles which have been subjected to a hydrophobizing treatment and further treated with a silicone oil or the like are added, or 61-24
JP-A-9059, JP-A-4-264453 and JP-A-5-346682 disclose a method in which hydrophobic-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 is used to impart conductivity to the toner, or to adhere or adhere to the toner surface for the purpose of 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.

In Japanese Patent Application Laid-Open No. 56-142540, conductive magnetic particles such as iron oxide, iron powder and ferrite are added to a high-resistance magnetic toner to accelerate the induction of electric charge to the magnetic toner. By doing so, a toner that achieves both developability and transferability has been proposed. Further, JP-A-61-2
No. 75864, JP-A-62-258472,
JP-A-61-141452, JP-A-02-120
Japanese Patent Application Laid-Open No. 865 discloses that graphite, magnetite, polypyrrole conductive particles, and polyaniline conductive particles are added to toner, and it is known that various kinds of conductive fine particles are added to toner.

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

In general, at this time, after the transfer, the toner remaining on the latent image carrier without being transferred onto the recording medium is cleaned by various methods and passed through a cleaning step of being stored as waste toner in a waste toner container. An image forming method in which the above steps are repeated has been used.

For this cleaning step, conventionally, blade cleaning, fur brush cleaning, roller cleaning, and the like have been used. In either method, the toner remaining after transfer is mechanically scraped off or dammed and collected in a waste toner container. Therefore, there has been a problem caused by such a member being pressed against the surface of the latent image carrier. For example, it is possible to wear the latent image carrier by strongly pressing the member to shorten the life. From the viewpoint of the apparatus, the provision of such a cleaning apparatus inevitably increases the size of the apparatus, which has been a bottleneck when aiming for a more compact apparatus.
Further, a system free of waste toner from the viewpoint of resource saving, reduction of waste, and effective use of toner, and a system excellent in fixing property and offset resistance have been desired.

On the other hand, as a system without waste toner, a technique called development / cleaning or cleaner-less has been proposed. However, the disclosure of the conventional technology relating to the development and cleaning or the cleanerless method mainly focuses on a positive memory, a negative memory, and the like due to the influence of residual toner on an image as disclosed in Japanese Patent Application Laid-Open No. 5-2287. there were.

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 techniques 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. I didn't.

Various methods are known for forming a visible image with toner. For example, as a method of visualizing an electric latent image, a cascade developing method, a pressure developing method, a magnetic brush developing method using a two-component toner composed of a carrier and a toner, and the like are known. A non-contact one-component development method in which the toner carrier is caused to fly from the toner carrier to the latent image carrier in a non-contact manner with the latent image carrier. A magnetic one-component developing method in which an electric field flies between the sleeves, and a contact one-component developing method in which a toner carrier is pressed against a latent image carrier to transfer toner by an electric field, are also used.

As a development method preferably applied to both development and cleaning or cleanerless, in the development and cleaning which conventionally has essentially no cleaning device, a constitution in which the surface of the latent image carrier is rubbed with toner and the toner carrier is essential. Therefore, many contact developing methods for contacting the toner or the latent image carrier with the toner 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 the latent image carrier is considered to be advantageous.

However, the development / cleaning or 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 photosensitive member or wear due to long-term use, and is insufficient for the durability characteristics. No solution has been made. Therefore, a developing and cleaning method using a non-contact developing method has been desired.

In an image forming method used in 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 an electrophotographic method, an electric latent image is formed by uniformly charging a photoreceptor using a photoconductive substance as a latent image carrier to a required polarity and potential, and then performing image pattern exposure. The method of forming is common.

Heretofore, a corona charger (corona discharger) has been often used as a charging device for uniformly charging a latent image carrier to a required polarity and potential (including a charge elimination process).
The corona charger is a non-contact type charging device, including a discharge electrode such as a wire electrode and a shield electrode surrounding the discharge electrode,
The discharge opening is disposed in a non-contact manner facing the image carrier as a member to be charged, and the surface of the image carrier is exposed to a discharge current (corona shower) generated by applying a high voltage to the discharge electrode and the shield electrode. The surface of the image carrier is charged in a predetermined manner.

In recent years, as a charging device for a member to be charged such as a latent image carrier, many contact charging devices have been proposed and put into practical use because of their advantages such as low ozone and low power as compared with corona chargers. ing. The contact charging device contacts a charged member such as an image carrier with a conductive charging member (contact charging member / contact charger) such as a roller type (charging roller), a fur brush type, a magnetic brush type, or a blade type. Then, a predetermined charging bias is applied to the contact charging member to charge the surface 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, (1) discharge charging mechanism and (2) direct injection charging mechanism, and each characteristic appears depending on which one is dominant.

(1) Discharge Charging Mechanism This is a mechanism for charging the surface of a member to be charged by a discharge phenomenon occurring in a minute gap between the contact charging member and the member to be charged. Since the discharge charging mechanism has a fixed discharge threshold value for the contact charging member and the member to be charged, it is necessary to apply a voltage higher than the charging potential to the contact charging member. Further, although the amount of generation is much smaller than that of the corona charger, it is in principle unavoidable to generate a discharge product, so that the harmful effects of active ions such as ozone are inevitable.

(2) Direct Injection Charging Mechanism This is a system in which the surface of the member to be charged is charged by injecting charges directly from the contact charging member to the member to be charged. It is also called direct charging, or 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, since direct injection charging is used, the contact property of the contact charging member with 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 described in (1) above.
Is dominant. The charging roller is manufactured using a conductive or medium-resistance rubber material 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 shape of the roller, and the uneven charging due to the adhered substance to be charged are inevitable.

FIG. 7 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, about -5
Charging starts after the discharge threshold of 00V. Therefore,
When charging to -500 V, apply a DC voltage of -1000 V or, in addition to the charging voltage of -500 V DC, apply an AC voltage of 1200 V between peaks so as to always have a potential difference greater than or equal to a discharge threshold. A method of converging the photoconductor potential to the charging potential is generally used.

More specifically, when a charging roller is pressed against an OPC photosensitive member having a thickness of 25 μm, applying a voltage of about 640 V or more increases the surface potential of the photosensitive member. At first, thereafter, the photoconductor surface potential linearly increases at a slope of 1 with respect to the applied voltage. This threshold voltage is defined as charging start voltage Vth. That is, in order to obtain the photoconductor surface potential Vd required for electrophotography, the charging roller needs a DC voltage higher than Vd + Vth. The 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, since the resistance value of the contact charging member fluctuates due to environmental fluctuations and the like, and Vth fluctuates when the film thickness changes due to shaving of the photoreceptor, the potential of the photoreceptor changes to a desired value. It was 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, since the essential charging mechanism uses a discharge phenomenon from the contact charging member to the photosensitive member, the charging is applied to the contact charging member as described above. The voltage is required to be higher than the surface potential of the photoreceptor, and a small amount of ozone is generated. Further, when AC charging is performed for uniform charging, ozone is further generated, vibration noise (AC charging noise) between the contact charging member and the photoconductor due to the electric field of the AC voltage, and the surface of the photoconductor due to discharge is generated. Degradation and the like became remarkable, and this was a new problem.

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 photosensitive member as a member to be charged. The photoreceptor surface is charged to a predetermined polarity and potential by applying a predetermined charging bias. This fur brush charging also has the charging mechanism described in (1) above.
Is dominant.

As the fur brush charger, a fixed type and a roll type are in practical use. A fixed type is 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 have the characteristics shown in FIG. 7B. Therefore, also in the case of the fur brush charging, in both the fixed type and the roll type, charging is performed by applying a high charging bias and using a discharge phenomenon.

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

In the case of the magnetic brush charging, the charging mechanism is dominated by the direct injection charging mechanism (2). The conductive magnetic particles constituting the magnetic brush portion have a particle size of 5 to 5
A direct injection charging can be uniformly performed by using a material having a thickness of 0 μm and providing a sufficient speed difference from the photosensitive member. As shown by C in the charging characteristic graph of FIG. 7, 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 a developing and cleaning method and a cleanerless image forming method. In the developing / cleaning method and the cleaner-less image forming method, the transfer residual toner remaining on the photoreceptor because it does not have a cleaning member directly contacts the contact charging member and adheres or mixes. Further, in the case of a charging method in which a discharge charging mechanism is dominant, the deterioration of the toner due to the discharge energy deteriorates the adhesion to the charging member. If a generally used insulating toner adheres to or mixes with the contact charging member, the charging property is reduced.

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

The reduction in the uniform chargeability of the charged body causes a decrease in the contrast and the uniformity of the electrostatic latent image after image exposure, and lowers the image density or increases fog.
In the developing / cleaning method and the cleaner-less image forming method, the charge polarity and charge amount of the transfer residual toner on the photoreceptor are controlled, and the transfer residual toner is stably collected in the developing process. The point is to prevent deterioration, and the charging polarity and the charging 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.

However, due to the negative polarity charging member when charging the negatively chargeable photoreceptor, even the toner remaining on the transfer along with the surface of the photoreceptor evenly oscillates to the positive polarity in the transfer step. The charge polarity can be adjusted to the negative side. Therefore, when the reversal development is used as a developing method, a negatively charged transfer residual toner remains in a bright portion potential portion of the toner to be developed, and a dark portion potential that should not be developed by the toner includes: Due to the development electric field, the toner is attracted toward the toner carrier, and the transfer residual toner is collected without remaining on the photoconductor having the dark portion potential. That is, by controlling the charging polarity of the toner remaining after transfer simultaneously with the charging of the photosensitive member by the charging member, the developing / cleaning and cleanerless image forming method is 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 transfer residual toner cannot be made uniform, and the developing member may not be uniform. It becomes difficult to collect the toner. Even if the toner remaining on the toner carrier is collected by mechanical force such as rubbing, if the charge of the transfer residual toner is not uniform, the chargeability of the toner on the toner carrier is adversely affected, and the developing property is deteriorated. Lower.

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

Japanese Patent Publication No. 7-99442 discloses a configuration in which a powder is applied to the contact surface of the contact charging member with the surface to be charged in order to prevent charging unevenness and perform stable uniform charging. However, contact charging member (charging roller)
Is driven by the object (photoreceptor) to rotate (no speed difference drive). Although the generation of ozone products is much less than that of a corona charger such as a scorotron, the charging principle is based on the roller charging described above. 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, the generation of ozone products due to discharge increases. Therefore, when the apparatus is used for a long time, adverse effects such as image deletion due to ozone products are likely to appear. Further, when the present invention is applied to a cleanerless image forming apparatus, it becomes difficult for the applied powder to uniformly adhere to the charging member due to mixing of transfer residual toner, and the effect of performing uniform charging is weakened.

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

However, the contact charging or proximity charging used here is based on the discharge charging mechanism, and has the above-mentioned problem due to the discharge charging, not the direct injection charging mechanism. Furthermore,
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 effect on the chargeability due to passing through a charging process, and the large amount of conductive No consideration is given to the recoverability of the fine particles and the transfer residual toner in the developing step, and the influence of the collected conductive fine particles and the transfer residual toner on the developing characteristics of the toner. Further, when the direct injection charging mechanism is applied to the contact charging, a necessary amount of the conductive fine particles is not supplied to the contact charging member, and a charging failure is caused by the influence of the transfer residual toner.

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

Japanese Patent Application Laid-Open No. 11-15206 discloses a method of forming a developing and cleaning image by improving the charge control characteristic of the transfer residual toner when passing through the charging member to improve the developing and cleaning performance. An image forming method using a toner having toner particles containing carbon black and a specific azo-based iron compound and inorganic fine powder has been proposed. Further, in the developing and cleaning image forming method, it has been proposed to improve the developing and cleaning performance by reducing the amount of transfer residual toner by using a toner having excellent transfer efficiency with a specified toner shape factor.

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 assist in controlling or recovering the transfer residual toner in the development and cleaning. There is also an image forming apparatus. Such an image forming apparatus exhibits good developing and cleaning properties and can greatly reduce the amount of waste toner, but increases costs and impairs the advantages of developing and cleaning in terms of downsizing.

On the other hand, JP-A-10-307456
Patent Application Publication No. JP-A-2005-122605, an image forming apparatus applied to a developing and cleaning 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, it is possible to obtain a developing / cleaning image forming apparatus which is capable of reducing the amount of waste toner without generating a discharge product, and which is advantageous in reducing the size and cost, resulting in poor charging, light blocking of image exposure, and the like. Alternatively, a good image free from diffusion can be obtained.

In Japanese Patent Application Laid-Open No. 10-307421, development and cleaning image formation using a direct injection charging mechanism of toner containing conductive particles having a particle diameter of 1/50 to 1/2 of the toner particle diameter is disclosed. There is disclosed an image forming apparatus which is applied to a method and in which conductive particles have a transfer promoting effect.

Further, in Japanese Patent Application Laid-Open No. Hei 10-307455, the particle size of the conductive fine powder is set to be equal to or smaller than the size of one pixel of the constituent pixels, and the particle size of the conductive fine powder is improved 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 made to have a size of about 5 μm in consideration of human visual characteristics in order to make it difficult to visually recognize the influence of a poorly charged portion on an image.
m, preferably 20 nm to 5 μm.

Further, according to Japanese Patent Application Laid-Open No. Hei 10-307458, when the particle size of the conductive fine powder is smaller than the toner particle size, the development of the toner is hindered at the time of development, or the developing bias is reduced. To prevent image defects and prevent image leakage, and by setting the particle size of the conductive fine powder to be larger than 0.1 μm,
A developing / cleaning image forming method using a direct injection charging mechanism which solves the problem of blocking conductive light by embedding conductive fine powder in an image carrier and realizing excellent image recording is described.

According to JP-A-10-307456, a conductive fine powder is externally added to a toner, and at least a conductive nip contained in the toner is provided at a nip portion between a flexible contact charging member and an image carrier. The fine powder adheres to the image carrier in the developing process and remains on the image carrier even after the transfer process. An obtained developing and cleaning image forming apparatus is disclosed.

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

Further, since high-speed fixing is performed in these image forming apparatuses, when a toner excellent in low-temperature fixing property is used, the durability of the toner is deteriorated, and the toner is easily fused to the photosensitive member. Matching with the toner to be used is not sufficient, for example, if a problem occurs, and there is room for further improvement.

[0086]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus which is hardly influenced by the environment, has stable charging performance, has no fog, has a high image density even when used for a long time, and has good image reproducibility and fixing ability. Image formation that is excellent in image quality and does not cause charging failure even after repeated use over a long period of time, and provides a stable and stable image even when toner particles with a small particle size are used to enhance resolution. It is to provide a method.

Further, in addition to the above objects, the present invention is advantageous in that the amount of waste toner can be significantly reduced without generating discharge products, is advantageous in reducing the size at a low cost, and stabilizes good chargeability. It is an object of the present invention to provide an image forming method which is capable of forming a developing and cleaning image which is obtained by the above method, has excellent transferability, and has excellent recoverability of transfer residual toner.

[0088]

According to the present invention, there is provided a charging step of charging an image carrier by applying a voltage to a charging member which forms a nip portion and comes into contact with the image carrier, and a charging surface of the image carrier. A latent image forming step of writing image information as an electrostatic latent image on the recording medium, a developing step of developing the electrostatic latent image with a magnetic toner carried on a toner carrier to form a toner image, and applying the toner image to a recording medium. An image forming method including at least a transfer step of transferring, wherein the magnetic toner is a toner particle including at least a binder resin, a wax, and a magnetic powder, an inorganic fine powder, and an average particle smaller than the toner particle. Conductive fine powder having a diameter of 0.96.
0 or more, the magnetic powder is a toner that is not substantially exposed to the surface of the toner particles, and the wax is a wax soluble in at least a monomer that is a component of the binder resin and an insoluble wax. And a magnetic toner used in the image forming method.

[0089]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an image forming method and a magnetic toner according to the present invention will be described in detail. First, the magnetic toner of the present invention will be described, and then the image forming method of the present invention using the toner will be described.

The magnetic toner (also simply referred to as “toner”) of the present invention is used in an image forming method using a contact charging method in which an image carrier is charged using a charging member that comes into contact with the image carrier. A magnetic toner having toner particles containing a resin, a wax, and a magnetic powder, having an average circularity of 0.960 or more, the magnetic powder is not substantially exposed on the surface of the toner particles, and the wax is at least bonded. It contains a wax that is soluble and insoluble in the monomer that is a component of the resin, and has an inorganic fine powder and a conductive fine powder smaller than the average particle diameter of the toner on the surface of the toner particles.

In the magnetic toner of the present invention, since the magnetic powder is not substantially exposed on the surface of the toner particles, the charge amount of the magnetic toner leaks unlike the magnetic toner in which the magnetic powder is exposed on the surface. Therefore, even if a large amount of conductive fine powder is present on the surface, it is possible to obtain a good image having a small image charge amount and a high image density.

Further, since the magnetic toner of the present invention contains a wax that is hardly compatible with the binder resin and a wax that plasticizes, the amount of wax present in the surface layer of the toner particles is appropriate, and Is easy to fix even if the resin softening point is high, and the toner fusion caused by exudation of wax is also improved. Further, since there is no exposure of the magnetic powder, an image with less fixing unevenness is easily obtained.

Further, since the average circularity and the mode circularity are very high, the magnetic toner forms fine spikes in the developing section, and the magnetic toner is uniformly charged one by one. It is possible to obtain an image.

First, the average circularity of the magnetic toner will be described. The average circularity is 0.960 or more, preferably 0.
A magnetic toner of 970 or more is very excellent in transferability.
It is considered that this is because the contact area between the toner particles and the image carrier is small, and the adhesive force of the toner particles to the image carrier due to the mirror image force, Van der Waals force, and the like is reduced. Therefore, if such a magnetic toner is used, the transfer rate is high, and the transfer residual toner is greatly reduced.Therefore, the magnetic toner in the contact portion between the charging member and the image carrier is very small, and the toner fusion is prevented. It is considered that image defects are significantly suppressed.

Further, since the magnetic toner having an average circularity of 0.960 or more, preferably 0.970 or more, has almost no edge on the surface, the friction at the contact portion between the charging member and the image carrier is reduced, and It is also mentioned that the shaving of the surface of the carrier is suppressed. These effects become more remarkable in an image forming method including a contact transfer step in which a dropout during transfer easily occurs. If the average circularity of the magnetic toner is less than 0.960, an image defect may occur due to an increase in friction in image formation.

In the circularity distribution of the magnetic toner,
When the mode circularity is 0.99 or more, it means that many of the toner particles have a shape close to a true sphere, and the above-mentioned action becomes more remarkable, and the transfer efficiency becomes extremely high, which is preferable. .

The average circularity of the magnetic toner of the present invention is used as a simple method for quantitatively expressing the shape of particles, and is an index of the degree of unevenness of the magnetic toner. In the present invention, the circularity (Ci) of each particle measured for a group of particles having a circle equivalent diameter of 3 μm or more is obtained by the following equation (1), and further, the totality of all the particles measured as shown by the following equation (2) is determined. The value obtained by dividing the total circularity by the total number of particles (m) is defined as the average circularity (Ca). When the magnetic toner has a perfect spherical shape, the value is 1.00. As the surface shape of the magnetic toner becomes more complicated, the average circularity becomes smaller.

[0098]

(Equation 1)

(Equation 2)

The mode circularity of the magnetic toner of the present invention is obtained by dividing the circularity from 0.40 to 1.00 into 61 by 0.01, and measuring the measured circularity according to each circularity. Is the lower limit value of the division range in which the frequency value is maximum in the circularity frequency distribution.

In the present invention, as a preferable measuring device for the average circularity and the like, there is a flow particle image analyzer “FPIA-1000” manufactured by Toa Medical Electronics.

As a specific method for measuring the average circularity and the mode circularity when using the above apparatus, about 5 mg of the magnetic toner is dissolved in 10 mL of water in which about 0.1 mg of a surfactant is dissolved.
mg to disperse to prepare a dispersion, and ultrasonic (20 KH
z, 50 W) to the dispersion for 5 minutes,
The average circularity and the mode circularity of a particle group having a circle equivalent diameter of 3 μm or more are determined by setting the particle size to 2,000 to 20,000 particles / μL.

Note that the above-mentioned measuring device “FPIA-1”
000 '', after calculating the circularity of each particle, in calculating the average circularity and the mode circularity, according to the circularity obtained the particles, the circularity is divided into classes obtained by dividing the circularity of 0.40 to 1.00 into 61, A calculation method of calculating the average circularity and the mode circularity using the center value and the frequency of the division point is used.

However, 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 practically negligible. In the present invention, each of the particles described above is used for data handling reasons such as short calculation time and simplification of calculation formulas. Such a calculation method partially modified using the concept of a calculation formula that directly uses the circularity of the above may be used.

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

In the magnetic toner of the present invention, the magnetic powder is not substantially exposed on the surface of the toner particles. Here, that the magnetic powder is not substantially exposed on the toner particle surface means that the ratio of the iron element content (B) to the carbon element content (A) present on the toner particle surface of the magnetic toner ( B / A) is less than 0.001, and the abundance ratio of the above elements on the surface of the toner particles can be measured by ESCA (X-ray photoelectron spectroscopy). Since the magnetic powder is not substantially exposed, scraping of the image carrier by the magnetic toner and fusion of the toner can be significantly reduced.

That is, in the image forming method including the contact charging step, when the magnetic toner having the magnetic powder exposed on the surface of the toner particles is used, the image carrier is more sharply shaved by the exposed magnetic powder. Easy to appear. However, if the B / A is less than 0.001 as described above, that is, if a magnetic toner in which the magnetic powder is substantially not exposed on the surface of the toner particles is used, the toner particles are transferred to the surface of the image carrier by a charging member or the like. The surface of the image carrier is hardly scraped even when pressed against, so that the scraping of the image carrier and toner fusion can be significantly reduced. Of course, the effect of the image forming method in which the contact transfer step is combined is remarkable, and an extremely high-definition image can be obtained for a long period of time.

The ESCA apparatus and measurement conditions preferably used in the present invention are as follows. Apparatus used: 1600S type X-ray photoelectron spectrometer manufactured by PHI Measurement conditions: X-ray source MgKα (400 W) Spectral area 800 μm diameter In the case of measuring with the above measuring apparatus and measuring conditions, PHI is determined from the peak intensity of each element measured. The surface atomic concentration (on a molar basis) is calculated as the content using a relative sensitivity factor provided by the company.

In the above measurement, the magnetic toner was subjected to ultrasonic cleaning to remove external additives such as inorganic fine powder adhering to the surface of the toner particles, and then the toner particles and the external additives were separated by magnetic force. Dry and measure. If it is difficult to remove the external additive, ultrasonic cleaning may be performed in an organic solvent such as isopropanol in which the toner particles do not dissolve.

A special magnetic toner in which a magnetic powder is contained only in a specific portion inside toner particles has already been disclosed in Japanese Patent Application Laid-Open No. 7-209904. However, JP-A-7-209904 does not mention the circularity of the disclosed magnetic toner. In the magnetic toner of the present invention, it is essential that the magnetic toner has a specific circularity.
It is not known whether similar effects can be obtained by using the magnetic toner described in JP-A-209904 in the same manner as the magnetic toner of the present invention.

Further, the configuration of the magnetic toner disclosed in JP-A-7-209904 is summarized as follows.
It has a structure in which a resin layer without magnetic powder is formed with a thickness of a certain amount or more near the surface of the toner particles. It means to do. In other words, in other words, when the average particle diameter of such a magnetic toner is small, for example, 10 μm, the volume in which the magnetic powder can exist is small, so that it is difficult to include a sufficient amount of the magnetic powder.

Further, in such a magnetic toner, in the particle size distribution of the magnetic toner, the ratio of the surface resin amount where no magnetic powder is present differs between the toner having a large particle diameter and the toner having a small particle diameter. Since the contents are different, the developing property and the transfer property also differ depending on the particle diameter of the magnetic toner, and the selective developing property depending on the particle diameter is easily seen.
Therefore, when printing is performed for a long time with such a magnetic toner, particles that are hard to develop and contain a large amount of magnetic powder, that is, a toner having a large particle diameter are likely to remain, resulting in a decrease in image density and image quality, and further, deterioration of fixability. Also leads to.

As can be seen from the above description, the preferred state of dispersion of the magnetic powder in the toner particles is a state in which the magnetic powder is present in the entire toner particles as much as possible without agglomeration. It forms the basis of the features of the magnetic toner of the invention. That is, a transmission electron microscope (TE
In the cross-sectional observation of the magnetic toner using M), when the projected area circle equivalent diameter of the toner particles is C and the minimum value of the distance between the magnetic powder and the toner particle surface is D, D / C ≦ 0.0
Another feature of the present invention is that the number of toner particles satisfying 2 is 50% or more.

In the present invention, the number of toner particles satisfying D / C ≦ 0.02 is preferably at least 50%, more preferably at least 65%. When the number of toner particles satisfying D / C ≦ 0.02 is less than 50%, no magnetic powder exists at least outside the boundary of D / C ≦ 0.02 in the majority of toner particles. become. Assuming that such particles are spherical, the space where no magnetic powder exists when one toner particle is the entire space is at least 11.5% on the surface of the toner particles.
Will exist. In the magnetic toner composed of such particles, various adverse effects as described above are likely to occur.

In the present invention, the D / C is obtained by calculating the circle equivalent diameter (C) of the toner particles from the cross-sectional area of the toner particles in the enlarged image, and the value is included in the range of ± 10% of the number average particle diameter. The minimum value (D) of the distance between the surface of the magnetic powder and the surface of the magnetic toner particle is measured and calculated for the corresponding particle. The ratio of the particles having a D / C value thus calculated of 0.02 or less is determined by the following equation. The number average particle size can be measured when measuring the particle size of the magnetic toner described below.

[0115]

(Equation 3)

In the D / C measurement, it is preferable to use a transmission electron microscope (TEM). Regarding a specific method of measuring D / C by TEM, a cured product obtained by sufficiently dispersing particles to be observed in a room temperature curable epoxy resin and then curing in an atmosphere at a temperature of 40 ° C. for two days is described. The method of observing as a flaky sample by a microtome as it is or after freezing is preferable. The micrograph at this time is preferably at a magnification of 10,000 to 20,000 times in order to perform highly accurate measurement. In the present invention, a transmission electron microscope (H-600 manufactured by Hitachi) is used as an apparatus, and an accelerating voltage of 1 is used.
It is preferable to observe at 00 kV and observe and measure using a micrograph with a magnification of 10,000 times.

The magnetic toner of the present invention has a magnetic field of 79.6 kA.
/ M (1000 Oersted) has a magnetization intensity of 1
It is preferably 0 to 50 Am ² / kg (emu / g).

The reason for defining the magnetization intensity at a magnetic field of 79.6 kA / m in the present invention is as follows.
As the quantity representing the magnetic characteristics of the magnetic powder, the intensity of magnetization at magnetic saturation (saturation magnetization) is used. In the present invention, the intensity of magnetization of the magnetic toner in the magnetic field acting on the magnetic toner at the time of image formation is reduced. is important. When a magnetic toner is applied to an image forming apparatus, a magnetic field acting on the magnetic toner is often commercially available in order not to increase the leakage of the magnetic field to the outside of the image forming apparatus or to keep the cost of the magnetic field source low. In the image forming apparatus, the magnetic field is 79.6 kA / m (1) as a typical value of the magnetic field actually acting on the magnetic toner during image formation.
000 Oersted) and a magnetic field of 79.6 kA / m
The intensity of the magnetization was specified.

Since the magnetic toner contains magnetic powder, the magnetic toner is prevented from leaking from the developing device by providing a magnetic force generating means in the developing device used in the developing step, and the magnetic toner is conveyed. In addition to improving the agitation or agitation properties, the provision of a magnetic force generating means so that a magnetic force acts on the toner carrier further improves the recovery of the transfer residual toner in a developing and cleaning method described later, and Since the magnetic toner forms ears on the toner carrier, it is easy to prevent the toner from scattering.

However, the magnetic field of the magnetic toner was 79.6 kA /
If the intensity of magnetization at m is less than 10 Am ² / kg, the above effects cannot be obtained, and if a magnetic force is applied on the toner carrier, the ears of the toner become unstable, and the charging of the magnetic toner becomes impossible. Image defects such as fog, image density unevenness, and defective transfer of residual toner due to non-uniformity are likely to occur. In addition, the conveyance of the magnetic toner to the toner carrier by the magnetic force tends to be insufficient.

When the magnetic strength of the magnetic toner in a magnetic field of 79.6 kA / m is larger than 50 Am ² / kg, when a magnetic force is applied to the magnetic toner, the magnetic toner significantly lowers its fluidity due to magnetic aggregation. As the transferability decreases, the transfer residual toner increases, and the tendency of the toner particles and the conductive fine powder to behave together increases. ,
The amount of the conductive fine powder interposed in the charging unit is also relatively reduced with respect to the amount of the transfer residual toner, so that fog and image stains due to the lowering of the charging property are easily caused.

When the amount of the magnetic powder is increased to further increase the strength of the magnetization, the fixing property tends to be deteriorated. In addition, since the magnetic toner of the present invention has an average circularity of 0.970 or more and a mode circularity of 0.99 or more, the spike of the toner on the toner carrier becomes thin and dense. Charging is made uniform, and fog is greatly reduced.

In the present invention, the magnetization strength of the magnetic toner may be measured with a magnetometer capable of appropriately setting the conditions of an external magnetic field, and preferably, a vibrating magnetometer VSM P-1-1.
0 (manufactured by Toei Kogyo KK) at 25 ° C. room temperature with an external magnetic field of 79.6 kA / m. The magnetic properties of the magnetic powder are measured at a room temperature of 25 ° C. and an external magnetic field of 796 kA / m.

The magnetic toner of the present invention has a weight average particle diameter of 3 μm in order to faithfully develop finer latent image dots in order to further improve the quality of the formed image.
It is preferably from 10 μm to 10 μm, more preferably from 4 μm to less than 8 μm.

In the case of a magnetic toner having a weight average particle size of less than 3 μm, transfer residual toner on the image carrier increases due to a decrease in transfer efficiency, and the image carrier is scraped during the contact charging step and toner fusion occurs. Control becomes difficult. Furthermore, in addition to an increase in the surface area of the entire magnetic toner, the fluidity and agitation properties of the powder decrease, and it becomes difficult to uniformly charge the individual toner particles, so that fog and transferability tend to deteriorate. This is not preferable for the magnetic toner used in the present invention, because it is liable to cause non-uniform unevenness of an image in addition to scraping and fusing.

The magnetic toner has a weight average particle diameter of 10 μm.
If it exceeds m, scattering is likely to occur in characters and line images, and it is difficult to obtain high resolution. Further, as the resolution of the apparatus increases, the magnetic toner having a size of 8 μm or more tends to deteriorate the reproduction of one dot.

In the case of applying to a developing and cleaning image forming method using a contact charging member like the magnetic toner of the present invention, the weight average particle diameter of the magnetic toner is set to be larger than 3 μm and smaller than 10 μm. Using a charging member that can reduce the generation of ozone, using a cleaner-less image forming method that does not generate waste toner, while maintaining good chargeability, greatly reduces the segregation of conductive fine powder and reduces image density It was clarified that the deterioration of the property can be improved to a level that does not cause a practical problem.

When the weight average particle diameter of the magnetic toner is 3 μm or less, the fluidity of the magnetic toner is reduced, and the tendency of the toner particles and the conductive fine powder to behave together increases. Transfer is facilitated, and the amount of conductive fine powder adhering to and mixing with the charging member and intervening in the charging portion is reduced. For this reason, the chargeability inhibition due to the transfer residual toner becomes relatively large, and it is impossible to maintain the chargeability, and the chargeability cannot be maintained, resulting in fog and image contamination.

The magnetic toner has a weight average particle diameter of 10 μm.
m or more, the charge amount of the toner particles tends to be greatly reduced due to the increase in the content of the conductive fine powder, and the amount of the conductive fine powder interposed in the charging unit is reduced by the density of the charging member on the image carrier. When the content of the conductive fine powder in the magnetic toner is set to such an extent that the proper contact property and contact resistance can be maintained, the chargeability of the toner particles is reduced, so that the developability of the entire magnetic toner is reduced, and Even a slight segregation of the conductive fine powder in the developing unit due to the collection of the magnetic toner having a significantly large ratio of the conductive fine powder by the cleaning may cause a remarkable reduction in image density due to a significant reduction in image density. In order to maintain more stable chargeability and developability, the weight average particle diameter of the magnetic toner should be 4 μm to 80 μm.
The following is preferred.

Here, the average particle size and the particle size distribution of the magnetic toner can be measured by various methods such as Coulter Counter TA-II or Coulter Multisizer (manufactured by Coulter Co., Ltd.). Interface (Nikkaki) and PC98 that output the number distribution and volume distribution using Coulter
It is preferable to perform measurement by connecting a 01 personal computer (manufactured by NEC). In addition, it is preferable to adjust a 1% NaCl aqueous solution using primary sodium chloride as the electrolytic solution. For example, ISOTON R-II (manufactured by Coulter Scientific Japan) can be used.

More specifically, in the above measurement, a surfactant, preferably an alkylbenzene sulfonate, was added as a dispersant in 100 to 150 mL of the electrolytic aqueous solution.
Add 1 to 5 mL, and further add 2 to 20 mg of the measurement sample.
The electrolytic solution in which the sample was suspended was subjected to a dispersion treatment for about 1 to 3 minutes using an ultrasonic disperser, and a 100 μm aperture was used as the aperture by the Coulter Multisizer.
The volume distribution and the number distribution are calculated by measuring the volume and the number of the toner particles having a size of μm or more. Then, a volume-based weight average particle diameter (D4) obtained from the desired volume distribution and a number-based number average particle diameter (D1) obtained from the number distribution are obtained.

The resistance of the toner particles of the magnetic toner of the present invention is preferably 10 ¹⁰ Ω · cm or more,
It is more preferably at least 0 ¹² Ω · cm. When the resistance of the toner particles is 10 ¹⁰ Ω · cm or more, the toner particles substantially show insulation. If the toner particles do not substantially exhibit insulation, it is difficult to achieve both developability and transferability. In addition, if the toner particles do not substantially exhibit insulation, electric charges are easily injected into the toner particles by a developing electric field, and the charge of the magnetic toner is disturbed, so that fog is easily generated.
The resistance of the toner particles is measured according to a method for measuring the resistance of the conductive fine powder described later.

The binder resin contained in the toner particles includes:
Styrene such as polystyrene and polyvinyltoluene and its substituted homopolymer; styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene- Ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-dimethylaminoethyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-methacrylic Acid ethyl copolymer,
Styrene-butyl methacrylate copolymer, styrene-
Dimethylaminoethyl methacrylate copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-
Isoprene copolymer, styrene-maleic acid copolymer,
Styrene-based copolymers such as styrene-maleic acid ester copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyethylene, polypropylene, polyvinyl butyral, silicone resin, polyester resin, polyamide resin, epoxy resin, polyacrylic acid Resin, rosin, modified rosin, temper resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, paraffin wax, carnauba wax, etc. 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.

In the present invention, the glass transition temperature (Tg) of the binder resin is preferably 50 to 70 ° C. Tg
If it is lower than 50 ° C., the storage stability of the magnetic toner tends to decrease, and if it is higher than 70 ° C., the fixability tends to deteriorate.

The magnetic toner of the present invention is also characterized in that the toner particles contain at least a wax soluble in the monomer which is a component of the binder resin and a wax insoluble in the monomer. As described above, the magnetic toner of the present invention is characterized in that the magnetic powder is not exposed on the surface of the toner particles, and the magnetic powder particles are present in the toner particles as uniformly as possible without agglomeration. It has been found that, since the powder has poor compatibility with the release agent, when a wax having a plasticizing effect is used, the wax tends to be intensively present in a portion where the proportion of the magnetic powder is small.

That is, if only a wax having a plasticizing effect is added to the magnetic toner for fixing at a low temperature, the amount of the wax increases relatively to the surface of the toner particles, and the image durability is extremely deteriorated although the fixing property at the low temperature is excellent. Do you get it. Accordingly, the present inventors have conducted intensive studies and found that a wax having a low compatibility with the binder resin can be finely dispersed without affecting the magnetic powder. By adding a small amount of wax moderately, it was found that the dispersibility of plastic wax in magnetic powder improved.
The present invention has been reached.

Further, since such a magnetic toner has no uneven distribution of wax in the toner particles, an alternating electric field is applied to the toner carrier, particularly in a high-temperature and high-humidity environment, so that the toner carrier and the image carrier are imaged. In the developing step (developing and cleaning step) in which development is performed by the reciprocating flying movement of the magnetic toner between the bodies, the toner fusion caused by the exudation of the wax is not affected by the numerous impacts with the image carrier. In addition, even when the method is applied to an image forming method using development and cleaning, toner fusion caused by wax oozing due to rubbing between the image carrier and the charging member is unlikely to occur.

The reason why the plastic wax dispersibility is improved in the present invention is not known in detail. However, even when the binder resin is in a molten state, a part of the wax which is substantially finely dispersed is observed. Since the incompatible wax is a crystallization nucleating agent for the plastic wax, it is expected that the wax dispersibility is improved.

The solubility and insolubility of the wax with respect to the monomers constituting the binder resin is determined by mixing the respective monomer components of the binder resin component at 70 ° C. lower than the fixing temperature. 10% by weight of wax is dispersed and heated or stirred for at least 5 minutes to determine the presence or absence of turbidity or phase separation. If turbidity or separation does not occur under the above conditions, soluble wax, turbidity or separation occurs. Was defined as an insoluble wax.

The above-mentioned monomer refers to a substance that is a component of the binder resin, and a monomer (such as a mixture of plural kinds of monomers) constituting the binder resin typified by a polymerizable monomer or the like. Including). In addition, the solubility of the wax in the binder resin is considered to depend on the physical properties of the monomers constituting the binder resin, but additives such as other resin compounds added for the purpose of modifying the magnetic toner and the like. Therefore, when determining the solubility of the wax, it is much more preferable to use a mixture of the above monomer and other main additives contained in the toner particles. preferable.

More specifically, in the case of performing a wax solubility test, a monomer such as a polymerizable monomer constituting a binder resin, which is a main component of a melting component, is used without using a binder resin. And a resin compound such as a polyester resin can be used in a compounding ratio in the toner particles. In addition, the solubility test of the wax can be performed by removing substances that hardly affect the physical properties such as the dispersibility of the wax, such as a low-mixing amount of a melted component or a solid component that does not melt.

The wax soluble in the monomer and the wax insoluble in the binder resin according to the present invention are described below.
Although different depending on the type of the binder resin to be used, various waxes can be used, and those shown below are preferable.

Examples of the soluble wax include alcohol wax, higher aliphatic alcohol, stearic acid,
Fatty acids such as palmitic acid or compounds thereof, alcohol alkylene oxide adduct wax, ester wax, hydrogenated castor oil, alcohol derivative wax, amide wax, ketone wax and oxides of these waxes, derivative waxes such as graft-modified products, paraffin Examples include hydrocarbon waxes such as waxes and microcrystalline waxes and oxides of these waxes, derivative waxes such as graft-modified products, montan waxes, animal waxes, plant waxes, petrolactam, and derivative waxes thereof. be able to.

Examples of the insoluble wax include petroleum waxes such as paraffin wax, microcrystalline wax and petrolactam, and oxides of these waxes, and derivative waxes such as block copolymers with vinyl monomers and graft-modified products. Synthetic waxes such as polyolefin wax, Fischer-Tropsch wax, montan wax, polyethylene wax and oxides of these waxes, block copolymers with vinyl monomers, derivative waxes such as graft-modified products, alcohol waxes, fatty acid waxes, Derivative waxes such as alcohol alkylene oxide adduct wax, ester wax, alcohol derivative wax, amide wax, ketone wax and oxides of these waxes, graft-modified products, Serial derivatives wax saponified, and the salts thereof may be exemplified.

Among the above waxes, ester waxes, paraffin waxes, micro waxes and the like which are soluble in the binder resin component monomer are small in terms of the influence on transferability and chargeability and the control of molecular weight distribution. It is particularly preferable to combine waxes such as crystallin wax, oxides / derivatives of these waxes, and synthetic waxes such as polyolefin wax, Fischer-Tropsch wax, montan wax, etc., and oxide / derivative waxes of these waxes.

Further, these waxes are obtained by sharpening the molecular weight distribution by using a press sweating method, a solvent method, a recrystallization method, a vacuum distillation method, a supercritical gas method, a molten liquid crystal deposition method, or the like, fatty acids, alcohols, and the like. A compound from which a low-molecular compound or other impurities have been removed is also preferably used in the present invention.

The content of the wax in the toner particles when the wax is used is preferably in the range of 0.5 to 50% by mass based on the binder resin in the toner particles. When the content of the wax is less than 0.5% by mass, the effect of suppressing low-temperature offset may not be sufficiently exhibited, and the content of the wax may be 50% by mass.
If the ratio exceeds the above range, the long-term storability will be deteriorated, the dispersibility of other toner materials will be deteriorated, and the fluidity of the magnetic toner may be deteriorated and the image characteristics may be deteriorated.

The content ratio of the wax was 0.5 parts by mass, when the amount of the soluble wax component was E parts by mass and the amount of the insoluble wax component was F parts by mass per 100 parts by mass of the binder resin. It is preferable that ≦ E / F ≦ 100. If the wax content ratio E / F is less than 0.5, the plasticization of the binder resin becomes insufficient, and the aggregation of the insoluble wax component tends to occur. Since development occurs, the image density tends to decrease particularly in a low-temperature and low-humidity environment. When the wax content ratio E / F exceeds 100, the effect of the crystal nucleating agent produced by the insoluble wax is reduced, so that although the low-temperature fixability is excellent, the durability is deteriorated. Fusion and the like are likely to occur.

It is preferable that at least one endothermic peak in the differential thermal analysis of each wax is in the range of 45 ° C. or more and 150 ° C. or less, more preferably 50 ° C. or more and 130 ° C. or less, from the viewpoint of fixability and manufacturability. . The endothermic peak is 45 ° C
If it is smaller, the storage stability of the magnetic toner tends to be insufficient, and an image defect due to fusion of the toner may occur. If the endothermic peak is higher than 150 ° C., the fixability of the magnetic toner tends to be insufficient, and the production efficiency may be lowered from the viewpoint of manufacturability.

In the present invention, the endothermic peak in the differential thermal analysis of the above wax is "ASTM D 3418".
-8 ". For the measurement, for example, it is preferable to use DSC-7 manufactured by PerkinElmer. More specifically, the temperature of the device detector is corrected using the melting points of indium and zinc, the calorific value is corrected using the heat of fusion of indium, the measurement sample is held using an aluminum pan, and the control sample is used as a control. Is measured at a heating rate of 10 ° C./min using an empty pan.

The magnetic toner of the present invention is characterized in that the toner particles contain a magnetic powder. The magnetic powder used in the magnetic toner of the present invention is phosphorus, cobalt, nickel,
Copper, magnesium, manganese, aluminum, may contain elements such as silicon, triiron tetroxide, γ-iron oxide, etc., which are mainly composed of iron oxide, and these are used alone or in combination of two or more. Can be These magnetic powders preferably have a BET specific surface area of ² to 30 m ² /
g, particularly preferably ^{3 to} 28 m ² / g, and more preferably 5 to 7 Mohs hardness.

Examples of the shape of the magnetic powder include an octahedron, a hexahedron, a sphere, a needle, a scale, and the like. It is preferable for increasing the concentration. The shape of such a magnetic powder can be confirmed by, for example, an SEM (scanning electron microscope). The volume average particle diameter of the magnetic powder is 0.01
To 1.0 μm, more preferably 0.05 to
0.5 μm is preferred.

When the volume average particle diameter of the magnetic powder is less than 0.01 μm, the blackness is remarkably reduced, and the coloring power of the black and white toner becomes insufficient. , The dispersibility tends to deteriorate. On the other hand, if the volume average particle size exceeds 1.0 μm, the coloring power may be insufficient similarly to a general coloring agent. In addition, particularly when used as a colorant for a small particle size toner, it is probabilistically difficult to disperse the same number of magnetic particles in individual toner particles, and the dispersibility tends to deteriorate.

As a preferred method of measuring the volume average particle diameter and the particle size distribution of the magnetic powder, a state in which the magnetic powder is sufficiently dispersed and a magnification of 30,000 times with a transmission electron microscope (TEM) is used. The method of measuring and finding the particle diameter of 100 magnetic powders in the field of view in the photograph of FIG.

The magnetic powder used in the magnetic toner of the present invention is preferably surface-treated by hydrolyzing a coupling agent in an aqueous medium. This surface treatment is closely related to the manufacturing process of the magnetic toner. The surface treatment of the magnetic powder will be described below.

The magnetic toner of the present invention can be produced by a pulverization method. However, the toner particles obtained by the pulverization method are generally amorphous, and the average particle size which is an essential requirement of the magnetic toner of the present invention is obtained. In order to obtain a physical property having a circularity of 0.960 or more, more preferably 0.970 or more, it is necessary to perform mechanical / thermal or some special treatment, resulting in poor productivity.

Therefore, in the present invention, it is preferable that the magnetic toner is produced by a polymerization method, particularly, a suspension polymerization method. In this suspension polymerization method, a polymerizable monomer and a colorant (and, if necessary, a polymerization initiator, a crosslinking agent, a charge control agent, and other additives) are uniformly dissolved or dispersed to prepare a monomer composition. After that, the monomer composition is dispersed in a continuous layer (for example, an aqueous phase) containing a dispersion stabilizer using a suitable stirrer, and simultaneously undergoes a polymerization reaction, so that toner particles having a desired particle size are obtained. Is what you get. The magnetic toner obtained by this suspension polymerization method (hereinafter, also referred to as “polymerized toner”)
Since the shape of each toner particle is substantially spherical, it is easy to obtain a magnetic toner having an average circularity of 0.960 or more and satisfying the physical property requirements essential to the present invention.

However, even if ordinary magnetic powder is contained in the polymerized toner, a large amount of free magnetic powder is generated, and the charging characteristics of the toner particles are significantly reduced. further,
Due to the strong interaction between the magnetic powder and water during the production of the suspension polymerization toner, it is difficult to obtain a magnetic toner having a circularity of 0.960 or more. This is because (1) the magnetic powder particles are generally hydrophilic and therefore easily exist near the interface between the monomer composition and the aqueous medium, and (2) the magnetic powder particles are stirred when the aqueous solvent is stirred. This is considered to be caused by the random movement, the surface of the suspended particles made of the monomer composition being dragged, and the shape being distorted and becoming difficult to be circular. In order to solve these problems, it is important to modify the surface characteristics of the magnetic powder particles.

Many proposals have been made regarding the surface modification of magnetic powder used in 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 No. 225102/224 proposes various silane coupling agent treatment techniques for magnetic powder.
No. 0660 discloses a technique for treating silicon element-containing magnetic particles with a silane coupling agent.

However, although the exposure of the magnetic powder from the surface of the toner particles is suppressed to some extent by these treatments, there is a problem that it is difficult to uniformly render the surface of the magnetic powder hydrophobic, and therefore, there is a problem. It is not possible to avoid coalescence of the powders or to generate magnetic powder particles that are not hydrophobized, which is insufficient to completely suppress the exposure of the magnetic powder.

As an example of using a hydrophobic magnetic iron oxide, Japanese Patent Publication No. 60-3181 proposes a magnetic toner containing a magnetic iron oxide treated with an alkyl trialkoxysilane. Although the electrophotographic properties of the magnetic toner have certainly been improved by the addition of the magnetic iron oxide, the surface activity of the magnetic iron oxide is inherently low, and coalesced particles are formed at the processing stage and hydrophobicity is not reduced. Uniform or not always satisfactory, further improvement is required for application to the magnetic toner of the present invention.

Further, when a large amount of a treating agent or the like or a highly viscous treating agent or the like is used, the degree of hydrophobicity is certainly increased, but the coalescence of the magnetic powder particles occurs and the dispersibility is reduced. On the contrary, it gets worse. Magnetic toners produced using such magnetic powders have non-uniform triboelectric charging properties, resulting in poor fog and poor transferability. As described above, in the polymerized toner using the conventional surface-treated magnetic powder, compatibility between hydrophobicity and dispersibility is not necessarily achieved, and such a polymerized toner is subjected to an image forming process including a contact charging step as in the present invention. Even if applied to the method, it is difficult to stably obtain a high-definition image.

Therefore, in the case of the magnetic powder used for the magnetic toner relating to the image forming method of the present invention, when the surface of the particle is hydrophobized, the magnetic powder particle is made to have a primary particle size in an aqueous medium. It is very preferable to use a method of performing a surface treatment while hydrolyzing a coupling agent while dispersing. In this hydrophobizing method, the magnetic powder particles are less likely to coalesce than in the gas phase, and the repelling action between the magnetic powder particles by the hydrophobizing process acts, so that the magnetic powder is substantially primary particles. Surface treatment. By performing such a hydrophobic treatment of the magnetic powder, the average circularity of the magnetic toner, the B / A described above, and the good dispersibility of the magnetic powder in the toner particles (D / C described above) can be improved. It is even more effective in realizing it.

The method of treating the surface of the magnetic powder 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 gaseous phase, magnetic powder particles can be 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 powder include a silane coupling agent and a titanium coupling agent. More preferably used is a silane coupling agent, having the general formula

## STR1 ## R _m SiY _n [In the formula, R represents an 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. ].

Examples of such a coupling agent include vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, methyltrimethoxysilane, methyltriethoxysilane, and isobutyltrimethoxysilane. Examples thereof include silane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane, hydroxypropyltrimethoxysilane, phenyltrimethoxysilane, n-hexadecyltrimethoxysilane, and n-octadecyltrimethoxysilane.

In particular, the formula

_Embedded image An alkyl represented by the formula: C _p H _{2p + 1} —Si— (OC _q H _{2q + 1} ) _{3 wherein} p represents an integer of 2 to 20, and q represents an integer of 1 to 3. The magnetic particles are preferably subjected to a hydrophobic treatment in an aqueous medium using a trialkoxysilane coupling agent.

When p in the above formula is smaller than 2, the hydrophobic treatment becomes easy, but it is difficult to impart sufficient hydrophobicity, and it becomes difficult to suppress the exposure of the magnetic particles from the toner particles. When p is larger than 20, the hydrophobicity is sufficient, but the coalescence of the magnetic powder particles is increased, and it is difficult to sufficiently disperse the magnetic powder particles in the toner particles. Transferability tends to deteriorate. Also,
When q is larger than 3, the reactivity of the silane coupling agent is reduced, and it is difficult to sufficiently perform the hydrophobic treatment.

In particular, alkyltrialkoxy wherein p 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 preferable to use a silane coupling agent.

The amount of the coupling agent to be treated is 0.05 to 20 parts by mass, preferably 0.1 to 100 parts by mass of the magnetic powder from the viewpoint of the effect of the treatment and the productivity.
The amount is preferably from 10 to 10 parts by mass.

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 weight based on water.
pH adjusters include inorganic acids such as hydrochloric acid.

In the surface treatment of the magnetic powder with the coupling agent, for example, a mixer having a stirring blade (specifically, a high shear mixing device such as an attritor or a TK homomixer) or the like is used. It is preferable to perform sufficient stirring so that the body particles become primary particles in the aqueous medium.

As magnetic properties of the magnetic powder, a magnetic field 79
Saturation magnetization is 10 to 200 Am ² / k under 5.8 kA / m
g, residual magnetization is 1 to 100 Am ² / kg, coercive force is 1 to
What is 30 kA / m is used. The magnetic powder used in the magnetic toner of the present invention is preferably used in an amount of 10 to 200 parts by mass with respect to 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 magnetic toner is poor, and it may be difficult to suppress fog. On the other hand, 20
If the amount is more than 0 parts by mass, the holding force due to the magnetic force on the toner carrier is increased, and the developing property is reduced. In addition, it becomes difficult to uniformly disperse the magnetic powder in the individual toner particles, and the fixing property is reduced. In some cases.

Here, an example of the magnetic powder used in the magnetic toner of the present invention will be introduced. When the magnetic powder is, for example, magnetite, it is produced by the following method.

First, an aqueous solution containing ferrous hydroxide is prepared by adding an equivalent such as sodium hydroxide in an amount equivalent to or more than the iron component to the aqueous ferrous salt solution. Adjust the pH of the prepared aqueous solution to pH 7 or more (preferably pH 8 to 1).
Air is blown in while maintaining the temperature at 0), and while the aqueous solution is heated to 70 ° C. or more, the oxidation reaction of ferrous hydroxide is performed to generate a seed crystal serving as a core of magnetic iron oxide particles.

Next, an aqueous solution containing about 1 equivalent of ferrous sulfate, based on the amount of the alkali previously added, is added to the slurry-like liquid containing the seed crystals. The reaction of ferrous hydroxide is promoted while blowing air while maintaining the pH of the solution at 6 to 10 to grow magnetic iron oxide particles around the seed crystal. The pH of the solution shifts to the acidic side as the oxidation reaction proceeds, but it is preferable that the pH of the solution is not less than 6. At the end of the oxidation reaction, adjust the pH of the solution, stir well so that the magnetic iron oxide becomes primary particles, add the coupling agent, mix and stir well, then stir, filter, dry and lightly disintegrate By doing so, hydrophobically treated magnetic iron oxide particles are obtained.

Alternatively, after completion of the oxidation reaction, 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, followed by sufficient stirring. The silane coupling agent may be added while performing the coupling treatment. 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 in the present invention.

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

The method for producing magnetic iron oxide by the aqueous solution method is as follows.
Generally, an aqueous solution having an iron concentration of 0.5 to 2 mol / L is used 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 magnetic toner made of the hydrophobic magnetic powder particles produced as described above, it is possible to achieve high image quality and high stability without causing abrasion of the photosensitive member and toner fusion. Become.

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 magnetic toner is produced by a direct polymerization method, a charge control agent having a low polymerization inhibitory property and having substantially no solubilized substance in an aqueous dispersion medium is particularly preferable.

Specific examples of the compound include a metal compound of an aromatic carboxylic acid such as salicylic acid, alkyl salicylic acid, dialkyl salicylic acid, naphthoic acid and dicarboxylic acid, a metal salt of azo dye or azo pigment as a negative charge control agent. Complex, a high molecular 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 high molecular compound having the quaternary ammonium salt in a side chain, a guanidine compound, a nigrosine compound, and an imidazole compound. As a method for incorporating the charge control agent into the toner, there are a method of adding the charge control agent inside the toner particles and a method of externally adding the charge control agent. In the present invention, either method may be used.

The amount of the charge control agent used is determined by the type of the binder resin, the presence or absence of other additives, and the method for producing the magnetic toner including the dispersion method, and is uniquely limited. However, it is preferable that the binder resin 100
It is used in the range of 0.1 to 10 parts by mass, more preferably 0.1 to 5 parts by mass with respect to parts by mass. However,
The magnetic toner relating to the image forming method of the present invention does not necessarily require the addition of a charge control agent, and does not necessarily include the charge control agent in the magnetic toner by actively utilizing the triboelectric charging during the development process. .

Further, other colorants may be used in combination with the magnetic toner of the present invention in addition to the magnetic powder. Coloring materials that can be used in combination include magnetic or non-magnetic inorganic compounds, known dyes and pigments. Specifically, for example, ferromagnetic metal particles such as cobalt and nickel, or alloys obtained by adding chromium, manganese, copper, zinc, aluminum and rare earth elements thereto, particles such as hematite, titanium black, nigrosine dye / pigment ,Carbon black,
Phthalocyanine and the like. These may also be used after treating the surface similarly to the magnetic powder.

Next, a method for producing the toner particles used in the present invention will be described. The method for producing the magnetic toner of the present invention is not particularly limited. In the present invention, as described above, toner particles can be produced by using a known production method such as a pulverization method or a polymerization method (particularly a preferable polymerization method is a suspension polymerization method).

First, the polymerization method will be described. In the magnetic toner of the present invention, a part or the whole of the toner particles is preferably produced by a polymerization method, and particularly preferably produced by a suspension polymerization method.

In the magnetic toner of the present invention obtained by the suspension polymerization method, generally, a magnetic powder, a releasing agent, a plasticizer, a charge controlling agent,
A crosslinking agent, a coloring agent and the like, as necessary, components necessary for the magnetic toner and other additives, for example, an organic solvent, a high-molecular polymer, a dispersant, and the like, which are added to reduce the viscosity of the polymer formed by the polymerization reaction, are appropriately added. In addition, the monomer system uniformly dissolved or dispersed by a disperser such as a homogenizer, a ball mill, a colloid mill, and an ultrasonic disperser is suspended in an aqueous medium containing a dispersion stabilizer.

At this time, the particle size of the obtained toner particles becomes sharper by using a high-speed disperser such as a high-speed stirrer or an ultrasonic disperser to quickly obtain the desired toner particle size. The timing of the addition of the polymerization initiator may be added when adding another additive in the polymerizable monomer,
You may mix immediately before suspending in an aqueous medium. Immediately after granulation and before the initiation of the polymerization reaction, a polymerization initiator dissolved in a polymerizable monomer or a solvent can be added. After granulation,
What is necessary is just to perform stirring using a usual stirrer to such an extent that the state of the particles is maintained and the floating and settling of the particles are prevented.

In the polymerization step, the polymerization is carried out at a polymerization temperature of 40 ° C. or higher, generally 50 to 90 ° C. When the polymerization is carried out in this temperature range, the release agent to be sealed inside, that is, the soluble wax is precipitated by phase separation while being finely dispersed under the influence of the insoluble wax, and the wax is appropriately dispersed. As it is, it is included in the toner particles. To consume the remaining polymerizable monomer,
At the end of the polymerization reaction, it is possible to raise the reaction temperature to 90 to 150 ° C.

After completion of polymerization, the polymerized toner particles are filtered, washed and dried by a known method, and an external additive such as inorganic fine powder is mixed with the obtained toner particles and adhered to the surface thereof, so that the magnetic toner is obtained. Obtainable. In addition, it is also a desirable embodiment of the present invention to insert a classifying step into the manufacturing process and cut coarse or fine powder.

Examples of the monomer (polymerizable monomer) which is a component of the binder resin in the magnetic toner of the present invention include the following.

Examples of the polymerizable monomer include styrene monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene and p-ethylstyrene, methyl acrylate, 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 and the like Acrylic esters, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, methacryl Phenyl, dimethylaminoethyl methacrylate, methacrylic acid esters other acrylonitrile such as diethylaminoethyl methacrylate,
Monomers such as methacrylonitrile and acrylamide are exemplified.

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

In the production of the toner particles used in the present invention, polymerization may be carried out by adding a resin to the monomer system. For example, hydrophilic functional groups such as amino groups, carboxylic acid groups, hydroxyl groups, sulfonic acid groups, glycidyl groups, and nitrile groups that cannot be used because monomers dissolve in aqueous suspensions to cause emulsion polymerization because of their water solubility. When it is desired to introduce the contained monomer component into the toner particles, a random copolymer of these with a vinyl compound such as styrene or ethylene, a block copolymer, or a graft copolymer, in the form of a copolymer,
Alternatively, it can be used 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 coexists in the toner particles, the above-mentioned wax component is phase-separated, the encapsulation becomes stronger, and the magnetic properties have good offset resistance, blocking resistance, and low-temperature fixability. A toner can be obtained.

When such a high molecular polymer containing a polar functional group is used, its average molecular weight is preferably 5,000 or more. When the molecular weight is 5,000 or less, especially 4,000 or less, the present polymer tends to concentrate near the surface, so that adverse effects on developability, anti-blocking properties and the like are likely to occur, which is not preferable. As the polar polymer, a polyester resin is particularly preferable.

Further, a resin other than the 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, and the like.
Styrene such as polystyrene and polyvinyltoluene and its substituted homopolymer; styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene- Ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-dimethylaminoethyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-methacrylic Acid ethyl copolymer,
Styrene-butyl methacrylate copolymer, styrene-
Dimethylaminoethyl methacrylate copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-
Isoprene copolymer, styrene-maleic acid copolymer,
Styrene-based copolymers such as styrene-maleic acid ester copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyethylene, polypropylene, polyvinyl butyral, silicone resin, polyester resin, polyamide resin, epoxy resin, polyacrylic acid Resin, rosin, modified rosin, temper resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin and the like can be used alone or in combination.

The amount of addition of these resins is as follows.
1 to 20 parts by mass relative to 0 parts by mass is preferred. When the amount is less than 1 part by mass, the effect of addition is small. On the other hand, when the amount is more than 20 parts by mass, it tends to be difficult to design various properties of the polymerized toner. Further, if a polymer having a molecular weight different from the molecular weight range of the toner particles obtained by polymerizing the monomer is dissolved in the monomer and polymerized, a magnetic toner having a wide molecular weight distribution and high offset resistance can be obtained. I can do it.

In the production of toner particles by a polymerization method, a polymerization initiator or the like for polymerizing the monomer can be used. Such a polymerization initiator having a half life of 0.5 to 30 hours at the time of the polymerization reaction, when the polymerization reaction is carried out at an addition amount of 0.5 to 20 parts by mass with respect to the polymerizable monomer, the molecular weight is increased. A polymer having a maximum between 10,000 and 100,000 can be obtained to give the toner the desired strength and suitable melting properties.

Examples of the polymerization initiator include 2,2'-azobis- (2,4-dimethylvaleronitrile) and 2,2'-
Azo such as azobisisobutyronitrile, 1,1'-azobis (cyclohexane-1-carbonitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, azobisisobutyronitrile -Based or diazo-based polymerization initiator, benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, cumene hydroperoxide, 2,4-
Peroxide-based polymerization initiators such as dichlorobenzoyl peroxide, lauroyl peroxide, and t-butylperoxy 2-ethylhexanoate are exemplified.

In the case of producing the toner particles used in the present invention by a polymerization method, a crosslinking agent may be added, and a preferable addition amount is 0.001 to 15% by mass. Here, as the cross-linking agent, compounds having two or more polymerizable double bonds are mainly used, for example, aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene, etc .; for example, ethylene glycol diacrylate, ethylene glycol diacrylate, etc. Carboxylic acid esters having two double bonds such as methacrylate and 1,3-butanediol dimethacrylate; divinyl compounds such as divinylaniline, divinyl ether, divinyl sulfide and divinyl sulfone; and having three or more vinyl groups Compound alone or as a mixture.

In the case of producing the toner particles used in the present invention by a polymerization method, known surfactants and organic / inorganic dispersants can be used as dispersion stabilizers. Above all, inorganic dispersants are unlikely to produce harmful ultrafine powder, and because of their steric hindrance, dispersion stability is obtained, so that even if the reaction temperature is changed, stability is not easily lost, washing is easy, and magnetic toner is not easily adversely affected. Therefore, it can be preferably used.

Examples of such inorganic dispersants include polyvalent metal phosphates such as calcium phosphate, magnesium phosphate, aluminum phosphate and zinc phosphate, carbonates such as calcium carbonate and magnesium carbonate, calcium metasilicate, calcium sulfate, and sulfuric acid. Examples include inorganic salts such as barium, and inorganic oxides such as calcium hydroxide, magnesium hydroxide, aluminum hydroxide, silica, bentonite, and alumina.

[0203] These inorganic dispersants can be used as polymerizable monomers 10
It is desirable to use 0.2 to 20 parts by mass alone with respect to 0 parts by mass, but 0.001 to 0.1 parts by mass of a surfactant is used in combination to obtain toner particles having a smaller particle size. You may.

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 the above-mentioned inorganic dispersant is used,
Although it may be used as it is, it is preferable to generate the inorganic dispersant particles in an aqueous medium in order to obtain finer particles. 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,
At the same time, a water-soluble sodium chloride salt is produced as a by-product, but when the water-soluble salt is present in the aqueous medium, the dissolution of the polymerizable monomer in water is suppressed, and it is difficult to generate an ultrafine toner due to emulsion polymerization. It is more convenient.

The above-mentioned dispersion stabilizer becomes an obstacle when removing the residual polymerizable monomer at the end of the polymerization reaction.
It is better to replace the aqueous medium at the end of the polymerization reaction or 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.

Next, the pulverizing method will be described. When the toner particles used in the present invention are produced by a pulverization method, a known method is used.For example, a binder resin, a magnetic powder, a release agent, a charge control agent, a coloring agent, etc. The necessary components and other additives are thoroughly mixed with a mixer such as a Henschel mixer or a ball mill, and then melt-kneaded using a heat kneader such as a heating roll, kneader, or extruder to mutually combine the resins. The toner particles can be obtained by dispersing or dissolving other toner particle materials such as magnetic powder in the melt, solidifying by cooling, pulverizing, classifying and, if necessary, surface treatment. Either the classification or the surface treatment may be performed first. In the classification step, it is preferable to use a multi-divider classifier in terms of production efficiency.

The pulverizing step can be performed by a method using a known pulverizing apparatus such as a mechanical impact type or a jet type.
In order to obtain a magnetic toner having a specific degree of circularity according to the present invention, it is preferable to further apply heat to pulverize or to perform auxiliary mechanical impact. Further, a lusting 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 Kogyo, a mechano-fusion system manufactured by Hosokawa Micron Corp. A method in which toner is pressed against the inside of a casing by centrifugal force using high-speed rotating blades, and a mechanical impact force is applied to toner particles by a force such as a compressive force or a frictional force, such as a device such as a hybridization system manufactured by Nara Machinery Co., Ltd. Is mentioned.

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 particles (T
g ± 10 ° C.) is preferable from the viewpoint of prevention of aggregation and productivity. More preferably, it is carried out at a temperature in the range of the glass transition point Tg ± 5 ° C. of the toner particles,
It is particularly effective for improving the transfer efficiency.

Further, the magnetic toner of the present invention can be obtained by atomizing a molten mixture into air using a disk or a multi-fluid nozzle described in Japanese Patent Publication No. Is typically represented by a dispersion polymerization method in which a toner is directly produced using an aqueous organic solvent in which a polymer obtained by dissolving is insoluble, or a soap-free polymerization method in which a magnetic toner is produced by direct polymerization in the presence of a water-soluble polar polymerization initiator. It can also be produced by a method of producing a magnetic toner using an emulsion polymerization method or the like.

[0212] The magnetic toner of the present invention is characterized in that, as a so-called external additive, an inorganic fine powder as a fluidizing agent and a conductive fine powder smaller than the average particle diameter of the toner particles are provided on the surface of the toner particles. I do. The inorganic fine powder used in the magnetic toner of the present invention preferably has an average primary particle size of 4 to 80 nm. The inorganic fine powder is added to improve the fluidity of the magnetic toner and to make the toner particles uniform in charge. However, by adjusting the inorganic fine powder to a hydrophobic treatment, the charge amount of the magnetic toner is adjusted, and the environmental stability is improved. It is also a preferable embodiment to provide functions such as improvement.

When the average primary particle size of the inorganic fine powder is larger than 80 nm, or when the inorganic fine powder having a particle size of 80 nm or less is not added, the transfer residual toner adheres to the charging member when it adheres to the charging member. This makes it difficult to obtain stable and good charging characteristics. Also, good fluidity of the magnetic toner cannot be obtained, and the charging of the toner particles tends to be uneven, increasing fog, lowering the image density,
Problems such as toner scattering may occur.

When the average primary particle diameter of the inorganic fine powder is smaller than 4 nm, the cohesiveness of the inorganic fine powder is increased, and the inorganic fine powder has a wide particle size distribution having a strong cohesive property which is difficult to be broken even by a crushing treatment. It easily behaves as an aggregate and easily causes image defects such as development of the aggregate and damage to the image carrier or the development carrier. To make the charge distribution of the toner particles more uniform, the average primary particle size of the inorganic fine powder should be 6 to
It is better to be 35 nm.

In the present invention, the average primary particle size of the inorganic fine powder is a photograph of the magnetic toner enlarged and taken by a scanning electron microscope, and is further analyzed by an elemental analysis means such as XMA attached to the scanning electron microscope. Measure the number of primary particles of inorganic fine powder adhering to or free from the toner particle surface by comparing 100 or more particles of the magnetic toner mapped with the element contained in the toner particles, and obtain the number average primary particle size It is measured by

The inorganic fine powder used in the present invention more preferably contains an inorganic fine powder having at least the above-mentioned average primary particle diameter selected from silica, titanium oxide, alumina, and double oxides thereof. About such inorganic fine powder,
Taking silica as an example, both so-called dry method or fumed silica produced by vapor phase oxidation of silicon halide and so-called wet silica produced from water glass or the like are used as silica. Although possible, dry silica having less silanol groups on the surface and inside the silica fine powder and having less production residue is preferable.

In the case of fumed silica, another metal halide such as aluminum chloride, titanium chloride or the like is used together with a silicon halide in the manufacturing process to form silica and another metal oxide. Composite fine powders (ie, double oxides) can be obtained, and the inorganic fine powders also include them.

The amount of the inorganic fine powder having an average primary particle size of 4 to 80 nm is 0.1 to 3.0% by mass based on the toner particles.
It is preferred that If the amount of the inorganic fine powder is less than 0.1% by mass, the effect may not be sufficiently exhibited,
If the content is 3.0% by mass or more, the fixability may be deteriorated.

[0219] The inorganic fine powder is preferably subjected to a hydrophobizing treatment in view of the characteristics under a high temperature and high humidity environment. When the inorganic fine powder added to the toner particles absorbs moisture, the charge amount of the toner particles is significantly reduced, and the toner is easily scattered.

As the treating agent for the hydrophobizing treatment, treating agents such as silicone varnish, various modified silicone varnishes, silicone oil, various modified silicone oils, silane compounds, silane coupling agents, and other organosilicon compounds and organotitanium compounds are used alone. Or in combination.

Among them, those treated with silicone oil are preferred, and more preferred are those obtained by treating the inorganic fine powder with a silane compound at the same time as or after the treatment with the silicone oil, and those treated with silicone oil even in a high humidity environment. This is good for keeping the charge amount of the particles high and preventing toner scattering.

As preferable treatment conditions for the inorganic fine powder, for example, a silylation reaction using a silane compound is performed as a first-step reaction to eliminate silanol groups by a chemical bond.
As a second stage reaction, a hydrophobic thin film can be formed on the surface by silicone oil.

The silicone oil has a viscosity at 25 ° C. of 10 to 200,000 mm ² / s, and 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 the silicone oil used, for example, dimethyl silicone oil, methylphenyl silicone oil, α-methylstyrene-modified silicone oil, chlorophenyl silicone oil, fluorine-modified silicone oil and the like are particularly preferable.

As a method for treating silicone oil,
For example, an inorganic fine powder treated with 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 the silicone oil in an appropriate solvent, adding a silica 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 amount of silicone oil to be treated 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 tends not to be obtained, and if it is too large, problems such as fogging may occur.

The average primary particle size used in the present invention is 80n.
m or less of the inorganic fine powder has a specific surface area by nitrogen adsorption measured by BET method is preferably one in 20~250m ² / g range, more preferably better ones 40 to 200 m ² / g. Regarding the measurement of the specific surface area, nitrogen gas is adsorbed on the sample surface using a specific surface area measuring device Autosorb 1 (manufactured by Yuasa Ionics) according to the BET method, and BE
The specific surface area is calculated using the T multipoint method.

In the magnetic toner of the present invention, a conductive fine powder is further used as an external additive. This is because the magnetic toner fused to the image carrier due to electrostatic factors can be easily removed by dielectric breakdown with the conductive fine powder, and the toner fusion can be suppressed.

Further, the content of the conductive fine powder in the whole magnetic toner is preferably 0.2 to 10% by mass. Since the magnetic powder of the present invention has substantially no magnetic powder exposed on the surface, the charge amount is high, and when the content of the conductive fine powder with respect to the entire magnetic toner is less than 0.2% by mass,
Developability tends to decrease. On the other hand, if the content is less than 0.2% by mass, when applying to an image forming method using development and cleaning, charging due to adhesion and mixing of insulating transfer residual toner to a charging contact charging member is performed. A sufficient amount of conductive fine powder to overcome the inhibition and make the charging of the image carrier good can not be interposed in the charging region in the nip portion of the charging member and the image carrier or in the vicinity thereof, In some cases, the chargeability is reduced, resulting in poor charging.

When the content is more than 10% by mass, the chargeability and developability of the magnetic toner in the developing section due to the excessive amount of the conductive fine powder collected by the developing and cleaning are reduced, The image density may be reduced or toner may be scattered. The content of the conductive fine powder with respect to the entire magnetic toner is more preferably 0.5 to 5% by mass.

Further, the conductive fine powder has a resistance of 10 ⁹ Ω ·
cm or less is preferable.
When the resistance of the conductive fine powder is larger than 10 ⁹ Ω · cm, the developability tends to decrease as in the above. Further, when applied to an image forming method using development and cleaning, conductive fine powder is interposed in a nip portion between a charging member and an image carrier or in a charging area in the vicinity thereof, and conductive fine powder of a contact charging member is used. Even if close contact with the image carrier through the body is maintained, the effect of accelerating the charge for obtaining good chargeability may not be obtained.

In order to sufficiently bring out the effect of accelerating the charging of the conductive fine powder and stably obtain good charging properties, the resistance of the conductive fine powder is limited to the contact with the surface of the contact charging member or the image carrier. It is preferably smaller than the resistance of the part. From such a viewpoint, the resistance of the conductive fine powder is more preferably 10 ⁶ Ω · cm or less.

The average particle size of the conductive fine powder is 0.5 to 5 μm.
m is preferable. If the average particle diameter of the conductive fine powder is small, the content of the conductive fine powder in the entire magnetic toner must be set small in order to prevent a decrease in developability. If the average particle size of the conductive fine powder is less than 0.5 μm, an effective amount of the conductive fine powder cannot be secured, and in the charging process, charging is inhibited due to adhesion and mixing of the insulative transfer residual toner to the contact charging member. The sufficient amount of conductive fine powder to overcome the above problem and make the charging of the image carrier satisfactory can not be interposed in the nip portion between the charging member and the image carrier or in the charging area in the vicinity of the nip portion. Tends to occur. From this viewpoint, the average particle size of the conductive fine powder is preferably 0.8
μm or more, more preferably 1.1 μm or more and less than 5 μm.

If the average particle size of the conductive fine powder is too large, the conductive fine powder dropped from the charging member blocks or diffuses the exposure light for writing the electrostatic latent image, thereby causing a defect of the electrostatic latent image. It tends to degrade image quality. Furthermore, if the average particle diameter of the conductive fine powder is large, the number of particles per unit weight decreases, so that the conductive fine powder is charged in consideration of the decrease and deterioration due to the drop of the conductive fine powder from the charging member. In order to continuously supply and interpose the conductive fine powder in the nip portion between the member and the image carrier or the charged area in the vicinity thereof, the charging member is densely connected to the image carrier via the conductive fine powder. In order to maintain the contact property and stably obtain good chargeability, the content of the conductive fine powder in the entire magnetic toner must be increased. However, if the content of the conductive fine powder is too large, the chargeability and developability of the magnetic toner as a whole, particularly in a high-humidity environment, are reduced, which may cause a reduction in image density and toner scattering. From such a viewpoint, the average particle diameter of the conductive fine powder is preferably less than 5 μm.

The conductive fine powder is preferably a transparent, white or light-colored conductive fine powder because the conductive fine powder transferred onto the transfer material is not conspicuous as fog. The conductive fine powder is also a transparent, white or light-colored conductive fine powder even in the sense of not hindering the exposure light in the latent image forming step, and more preferably, the transmittance of the conductive fine powder to the exposure light is higher. It is good to be 30% or more.

In the present invention, the light transmittance of the conductive fine powder is preferably measured by the following procedure. More specifically, 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 a net light amount from the light amount when the particles adhere to only the film. Actually, it can be measured using a 310T transmission densitometer manufactured by X-Rite.

Examples of the conductive fine powder in the present invention include fine carbon powder such as carbon black and graphite; fine metal powder such as copper, gold, silver, aluminum and nickel; zinc oxide, titanium oxide, tin oxide and aluminum oxide. , Indium oxide, silicon oxide, magnesium oxide,
Metal oxides such as barium oxide, molybdenum oxide, iron oxide, and tungsten oxide; metal compounds such as molybdenum sulfide, cadmium sulfide, and potassium titanate, or composite oxides of these, etc., whose particle size and particle size distribution are adjusted as necessary It can be used by doing. Among them, fine particles having at least the surface of an inorganic oxide such as zinc oxide, tin oxide and titanium oxide are particularly preferable.

Further, for the purpose of controlling the resistance value of the conductive fine powder, etc., a metal oxide containing 0.1 to 5% by mass of an element such as antimony or aluminum different from the main metal element of the conductive fine powder. Fine particles having a conductive material on the surface can also 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. In addition, as the conductive fine powder, those in which the inorganic oxide is of an oxygen deficiency type are also preferably used.

The following can be exemplified as such conductive fine powder. Examples of commercially available conductive titanium oxide fine particles treated with tin oxide and antimony include EC-300 (Titanium Industry Co., Ltd.) and ET-30.
0, HJ-1, HI-2 (Ishihara Sangyo Co., Ltd.),
WP (Mitsubishi Materials Corporation) and the like.

Commercially available antimony-doped conductive tin oxides include, for example, T-1 (Mitsubishi Materials Corporation) and SN-100P (Ishihara Sangyo Co., Ltd.), and commercially available stannic oxides include SH- S (Japan Chemical Industry Co., Ltd.). Particularly preferred are metal oxides containing aluminum and / or oxygen-deficient metal oxides from the viewpoint of developability.

The volume average particle size and the particle size distribution of the conductive fine powder used in the present invention can be appropriately measured by a suitable measuring method depending on the target particle size. For example, LS-230 type laser manufactured by Coulter Inc. Attach a liquid module to the diffraction type particle size distribution analyzer
It can be measured in a measurement range of 4 to 2000 μm.
As a measurement method, a trace amount of a surfactant was added to 10 mL of pure water, a 10 mg sample of the conductive fine powder was added thereto, and the mixture was dispersed for 10 minutes with an ultrasonic dispersing machine (ultrasonic homogenizer). The measurement was carried out once per second.

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 particle of the conductive fine powder has a desired particle size and particle size distribution at the time of manufacturing. In addition to the setting method, a method of aggregating small particles of primary particles, a method of pulverizing large particles of primary particles or a method by classification, and the like, are further possible. A method of attaching or immobilizing conductive particles to part or all of the surface, 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 are also possible. It is also possible to adjust the particle size and particle size distribution of the conductive fine powder by combining the above methods.

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

In the present invention, the resistance of the conductive fine powder can be measured by a so-called tablet method which is well known as a method of measuring the resistance of the powder. More specifically, it was measured and normalized by the tablet method. That is, about 0.5 g of a powder sample was placed in a cylinder having a bottom area of 2.26 cm ² , and 15 kg of pressure was applied to the upper and lower electrodes, and at the same time, a voltage of 100 V was applied to measure the resistance value. Was calculated.

The magnetic toner of the present invention further has a primary particle size of more than 30 nm (preferably, a specific surface area of less than 50 m ² / g), and more preferably a primary particle size of 50 nm or more, for the purpose of improving lubricity. Preferably, the specific surface area is 30 m ²
/ G) is also one of the preferred forms. As such fine particles, for example, spherical silica particles, spherical polymethylsilsesquioxane particles, and spherical resin particles are preferably used.

In the magnetic toner of the present invention, other additives such as lubricant powders such as Teflon (registered trademark) powder, zinc stearate powder, polyvinylidene fluoride powder, or the like, as long as they do not substantially adversely affect the toner. Abrasives such as cerium oxide powder, silicon carbide powder, strontium titanate powder, or a fluidity imparting agent such as titanium oxide powder, aluminum oxide powder, an anti-caking agent,
Organic fine particles of an opposite polarity and inorganic fine powder can be used in a small amount as a developability improver. These additives can be used after the surface is subjected to a hydrophobic treatment.

The magnetic toner of the present invention is preferably applied to an image forming method such as a developing / cleaning image forming method or a cleanerless image forming method.

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 toner particles in the developing and cleaning image forming method will be described.

The conductive fine powder contained in the magnetic toner is as follows:
During development of the electrostatic latent image on the image carrier in the developing step, an appropriate amount moves to the image carrier together with toner particles. The toner image on the image carrier is transferred to the recording medium in a transfer step. A part of the conductive fine powder on the image carrier also adheres to the recording medium side, but the rest remains adhered and held on the image carrier.

When transfer is performed by applying a transfer bias having a polarity opposite to that of the magnetic toner, the magnetic toner is attracted to the recording medium and is positively transferred, but the conductive fine powder on the image carrier is conductive. Due to the nature, it does not positively transfer to the recording medium side, and a part adheres to the recording medium side, but the rest remains adhered and held on the image carrier.

In an 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 carried as it is to the charging portion, which is a nip portion between the image carrier and the charging member, by the movement of the image carrier surface and transferred to the charging member. Adhere and mix. Therefore, the contact charging of the image carrier is performed in a state where the conductive fine powder is interposed in the nip portion between the image carrier and the charging member.

The presence of the conductive fine powder makes it possible to maintain the close contact property and contact resistance of the charging member with the image carrier irrespective of contamination due to the adhesion or mixing of the transfer residual toner to the charging member. The image carrier can be favorably charged by the charging member.

The transfer residual toner adhering to and mixed into the 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 gradually from the image bearing member. It is discharged upward, reaches the developing section with the movement of the image carrier surface, and is developed and cleaned (collected) in the developing step.

Further, as the image formation is repeated, the conductive fine powder contained in the magnetic 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 charged part after being transported, even if the conductive fine powder is dropped or deteriorated due to dropping or the like in the charged part, it is prevented that the chargeability is reduced. And good chargeability is stably maintained.

A further problem to be solved is that the conductive fine powder is positively present in the nip portion between the image carrier and the charging member, and the charging inhibition is caused by the adhesion and mixing of the insulative transfer residual toner to the charging member. When the necessary amount of conductive fine powder is contained in the magnetic toner in order to overcome the above problem and charge the image carrier satisfactorily, the image density decreases when the magnetic toner is used in the toner cartridge until the amount of the magnetic toner decreases. Alternatively, good image quality may not be maintained due to an increase in fog.

Even in the conventional image forming apparatus having a cleaning mechanism, when the conductive fine powder is contained in the magnetic toner, the conductive fine powder is selectively consumed in the developing step, or conversely, the conductive fine powder is selectively consumed. Due to segregation of the conductive fine powder in the magnetic toner due to the remaining fine powder, the image density may decrease or the fog may increase when the magnetic toner is used in the toner cartridge until the amount decreases. There is. For this reason, it is possible to reduce the selective consumption or segregation of the conductive fine powder by, for example, fixing the conductive fine powder to the toner particles, and to prevent a decrease in image density due to a decrease in image density and an increase in fog. Are known.

However, when the magnetic toner containing the conductive fine powder is applied to the developing and cleaning image forming method, the segregation of the conductive fine powder has a greater effect on the image characteristics. That is, as described above, the conductive fine powder contained in the magnetic toner is transferred to the image carrier along with the toner particles in an appropriate amount in the developing process, and then the conductive fine powder on the image carrier is also transferred in the transfer process. The portion adheres to the recording medium side, but the rest remains adhered and held on the image carrier.

When the transfer is performed by applying a transfer bias, the toner particles are attracted to the recording medium and actively transferred, but the conductive fine powder on the image carrier is conductive. It does not positively transfer to the recording medium side, and a part adheres to the recording medium side, but the rest remains adhered and held on the image carrier.

In the image forming method of the present invention, since the cleaner is not used, the transfer residual toner remaining on the surface of the image carrier after the transfer and the above-mentioned residual conductive fine powder adhere and mix into the charging member. At this time, the ratio of the amount of the conductive fine powder adhering to and mixing into the charging member with respect to the transfer residual toner is determined by the difference in transferability between the conductive fine powder and the toner particles. Clearly higher than the volume ratio.

In this state, the conductive fine powder adhering to and mixed into the charging member is gradually discharged from the charging member together with the transfer residual toner onto the image carrier, moves to the image carrier surface, and reaches the developing section. Developed and cleaned (collected). That is, by developing and cleaning,
By collecting the magnetic toner having an extremely large ratio of the conductive fine powder, segregation of the conductive fine powder is greatly accelerated,
This leads to a remarkable reduction in image density due to a remarkable reduction in image density.

On the other hand, as in the case of an image forming apparatus having a conventional cleaning mechanism, if an attempt is made to reduce the segregation of the conductive fine powder by fixing the conductive fine powder to the toner particles, the transfer process is also performed. Since the conductive fine powder behaves with the toner particles, it is transferred to the recording medium side together with the toner particles, and the conductive fine powder cannot adhere to or mix with the charging member and intervene in the charging portion.
Or even if interposed, the amount of conductive fine powder interposed with respect to the transfer residual toner amount becomes insufficient, and the chargeability cannot be maintained by overcoming the chargeability inhibition by the transfer residual toner,
In addition, it is not possible to maintain the close contact property and contact resistance of the charging member with the image carrier, and the chargeability of the image carrier by the charging member is reduced, resulting in fog and image contamination. The above-described difficulties have been encountered in applying a magnetic toner containing conductive fine powder to a developing and cleaning image forming method using a charging member.

By using the magnetic toner of the present invention,
In development and cleaning image forming method or cleaner-less image forming method, segregation of conductive fine powder is greatly reduced while maintaining good chargeability, and image quality such as image density is reduced to a level that does not cause practical problems. Can be improved.

Next, an image forming method of the present invention using the above-described magnetic toner will be described. The image forming method according to the present invention includes a charging step of charging the image carrier by applying a voltage to a charging member that forms a nip portion with the image carrier and contacts the same, and an electrostatic latent image on the charged surface of the image carrier. A latent image forming step of writing image information, a developing step of developing the electrostatic latent image with a magnetic toner carried on a toner carrier to form a toner image, and a transferring step of transferring the toner image to a recording medium , Wherein the magnetic toner described above is used.

The charging step in the image forming method of the present invention is characterized in that the image bearing member is charged by applying a voltage to a charging member that forms a nip portion and comes into contact with the image bearing member. This charging step is preferably a step of charging the image carrier in a state where at least 10 ³ / mm ² or more conductive fine powders are interposed in the nip portion between the charging member and the image carrier.

If the amount of the conductive fine powder in the nip portion between the image carrier and the charging member is too small, the lubricating effect of the fine powder cannot be sufficiently obtained, and the friction between the image carrier and the charging member is reduced. When it is large, it tends to be difficult when the charging member is driven to rotate with a speed difference between the image carriers. That is, the driving torque becomes excessively large, and the surface of the charging member or the image bearing member is scraped if it is rotated forcibly. Further, the effect of increasing the chance of contact by the conductive fine powder may not be obtained, so that it is difficult to obtain sufficient charging performance. On the other hand, if the intervening amount is too large, the detachment of the conductive fine powder from the charging member is remarkably increased, which tends to adversely affect image formation.

According to experiments, the amount of conductive fine powder interposed was 10
^It is preferably at least ³ / mm ² , more preferably at least 10 ⁴ / mm ²
mm ² or more is good. If it is lower than 10 ³ / mm ² , a sufficient lubricating effect and an effect of increasing the contact chance cannot be obtained, and the charging performance may decrease. If it is lower than 10 ⁴ particles / mm ² , the charging performance may be reduced when the amount of 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.

It is needless to say that at the time of charging, uniform contact charging is required at least than this recording resolution. However, regarding the visual characteristics of the human eye, a spatial frequency of 10
Above cycles / mm, the number of discrimination gradations on the image approaches 1 without limit. That is, density unevenness cannot be identified. If this property is positively utilized, when the conductive fine powder is adhered on the image carrier, the conductive fine powder is present at a density of at least 10 cycles / mm on the image carrier, and direct injection charging is performed. That would be good. Even if micro charge failure occurs where no conductive fine powder is present, density unevenness on an image caused by the charge failure occurs in a spatial frequency region exceeding human visual characteristics. Then there will be no problem.

Whether the charging failure as density unevenness is recognized on the image when the coating density of the conductive fine powder is changed is determined by applying a small amount of the conductive fine powder (for example, 10 / Mm ² ), the effect of suppressing the occurrence of charging unevenness is recognized, but it is still insufficient in terms of whether density unevenness on an image is acceptable to humans.

However, if the coating amount is 10 ² / mm ² or more, a favorable result can be rapidly obtained in the objective evaluation of the image. Further, by increasing the coating amount by at least 10 ³ / mm ^2, there is no problem on the image due to poor charging.

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

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

The upper limit of the amount of the conductive fine powder applied is as follows:
Until the conductive fine powder is applied more evenly on the image carrier, application of more than that does not improve the effect, but adversely affects the exposure light source by blocking or scattering.

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 forcibly described, the conductive fine powder is uniformly formed on one layer of the image carrier. The amount applied is the upper limit. The amount of conductive fine powder is 5
When the density exceeds × 10 ⁵ / mm ² , the drop of the conductive fine powder to the image carrier increases remarkably, and the exposure amount to the image carrier becomes insufficient regardless of the light transmittance of the conductive fine powder itself. There is a tendency. When the density is 5 × 10 ⁵ particles / mm ² or less, the amount of the conductive fine powder that falls off can be suppressed to be low, and the inhibition of exposure can be improved. Since was when measuring the abundance of the conductive fine powder which is falling onto the image carrier 10 ² to 10 ⁵ cells / mm ² in the intervening weight range, 10 ⁴ as the abundance is not imaged on the harmful effects ~ 5 × 10 ⁵ /
An intervening amount of mm ² is preferred.

A method for measuring the amount of conductive fine powder present in the charging nip and the amount of conductive fine powder present on the image carrier in the latent image forming step will be described. It is desirable that the interposed amount of the conductive fine powder is directly measured at the contact surface portion between the charging member and the image carrier, but when a speed difference is provided between the surface of the charging member forming the nip portion and the surface of the image carrier, Many of the particles (transfer residual toner, conductive fine powder, etc.) existing on the image carrier before coming into contact with the charging member are peeled off by the charging member that comes in contact with moving in the opposite direction. The amount of particles on the surface of the charging member immediately before reaching the surface portion was defined as the intervening amount.

Specifically, the rotation of the image carrier and the elastic conductive roller is stopped in a state where no charging bias is applied,
The surfaces of the image carrier and the elastic conductive roller are surface-mounted with a video microscope (OVM1000N manufactured by OLYMPUS) and a digital still recorder (SR-310 manufactured by DELTAS).
0). With respect to the elastic conductive roller, the elastic conductive roller is brought into contact with the slide glass under the same condition as that of the image carrier, and the contact surface is viewed from the back of the slide glass with a video microscope at 10 positions with a 1000-fold objective lens. The above was taken.

In order to separate individual particles from the obtained digital image, binarization processing was performed with a certain threshold value, and the number of regions where particles exist was measured using desired image processing software. In addition, the abundance on the image carrier was measured by photographing the image carrier with the same video microscope and performing the same processing.

Further, the charging step in the present invention is a step in which the surface of the charging member forming the nip portion and the surface of the image carrier move with a relative speed difference to charge the image carrier. This is preferable in that the chance of contact of the conductive fine powder with the image carrier in the nip portion between the charging member and the image carrier is significantly increased, higher contact properties can be obtained, and the direct injection charging property is improved.

By interposing conductive fine powder in the nip portion between the charging member and the image carrier, a large torque is applied between the charging member and the image carrier due to the lubricating effect (friction reducing effect) of the conductive fine powder. It is possible to provide the speed difference without increasing the size of the charging member and the surface of the charging member and the image carrier.

As a configuration for providing a speed difference, a configuration in which a charging member is rotationally driven to provide a speed difference between the image carrier and the charging member can be mentioned.

In the charging step of the present invention, the surface of the charging member and the surface of the image holding member are transferred to the charging member in order to temporarily collect the transfer residual toner on the image bearing member carried to the charging section and level the toner. It is preferable to charge the image carrier while moving in opposite directions. For example, rotating the charging member,
Further, it is preferable that the rotation direction is configured to rotate in a direction opposite to the moving direction of the surface of the image carrier. That is,
It is possible to perform direct injection charging with superiority by temporarily separating the transfer residual toner on the image carrier by reverse rotation and performing 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 charging property 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. The peripheral speed ratio described here is

The peripheral speed ratio (%) = (the peripheral speed of the charging member / the peripheral speed of the image carrier) × 100 (the peripheral speed of the charging member moves in the same direction as the surface of the image carrier at the nip portion). When it is positive).

In the charging step in the image forming method of the present invention, the above-mentioned image carrier (charging member) is charged with a conductive charging member such as a roller type (charging roller), a fur brush type, a magnetic brush type, or a blade type. (Contact charging member / contact charger), and a contact charging device that applies a predetermined charging bias to the charging member to charge the image carrier surface to a predetermined polarity and potential. In order to temporarily recover the transfer residual toner on the image carrier and carry conductive fine powder to perform superior direct injection charging, an elastic conductive roller, which is a flexible member as a charging member, or a rotatable roller It is preferable to use a suitable charging brush roll.

In the present invention, it is preferable that the charging member has elasticity in providing a nip portion between which the conductive fine powder is interposed between the charging member and the image carrier, and that a voltage is applied to the charging member. It is preferable that the toner is electrically conductive to charge the image carrier. Therefore, the charging member is composed of a roller member having elasticity and conductivity, a magnetic brush charging member having a magnetic brush portion in which magnetic particles are magnetically constrained, and the magnetic brush portion being brought into contact with the image carrier, or a conductive fiber. It is preferably a brush member such as a charged brush.

In the case where a roller member is used as the charging member, the charging step in the present invention has an Asker C hardness of 50.
It is preferable that the image bearing member is charged by applying a voltage to a conductive roller member having a temperature equal to or lower than the temperature.
If the hardness of the roller member is too low, the shape is not stable, so that the contact property with the image carrier deteriorates, and furthermore, the conductive fine powder is interposed in the nip portion between the charging member and the image carrier. There is a tendency that the surface layer of the roller member is scraped or damaged, and stable chargeability cannot be obtained. On the other hand, if the hardness is too high, not only the charging nip portion cannot be ensured with the image carrier, but also the microscopic contact with the surface of the image carrier tends to deteriorate. For these reasons, the hardness of the roller member is more preferably 25 to 50 degrees in Asker C hardness. The Asker C hardness is, specifically,
For example, it can be measured by using an Asker hardness tester type C manufactured by Kobunshi Keiki Co., Ltd. and measuring under a load of 500 g.

It is important that the roller member has elasticity so as to obtain a sufficient contact state with the image carrier and, at the same time, functions as an electrode having a resistance low enough to charge the moving image carrier. On the other hand, it is necessary to prevent voltage leakage when a defective portion such as a pinhole exists in the image carrier.

When an electrophotographic photosensitive member is used as the image carrier, in order to obtain sufficient chargeability and leakage resistance, the charging step in the present invention requires that the resistance be 10 ³ Ω · cm or more and 10 ⁸ Ω · c.
Preferably, the step is a step of charging the image carrier by applying a voltage to a roller member of m or less. More preferably, the resistance of the roller member is 10 ⁴ Ω · cm or more and 10 ⁷ Ω · cm or less. Roller resistance is 30mm in diameter so that a total pressure of 1kg is applied to the core of the roller.
In the present invention, it is preferable that a voltage of 100 V is applied between the cored bar and the aluminum drum while the roller is pressed against the cylindrical aluminum drum.

The roller member is manufactured by, for example, forming a medium resistance layer of rubber or foam as a flexible member on a cored bar. The medium resistance layer is formulated with a resin (eg, urethane), conductive particles (eg, carbon black), a sulfide agent, a foaming agent, and the like, and is formed in a roller shape on a cored bar. Thereafter, if necessary, the conductive elastic roller can be manufactured by cutting and polishing the surface to adjust the shape.

The surface of the roller preferably has minute cells or irregularities in order to interpose conductive fine powder. The roller member has an average cell diameter of 5 in spherical form.
It is preferable that at least the surface of the roller member has a depression of about 300 μm, and the porosity of the roller member surface having the depression as a void is 15 to 90%. When the cell diameter is outside the above range, the retention of the conductive fine powder tends to be insufficient, and when the porosity is outside the above range, the holding amount of the conductive fine powder tends to be insufficient, and both of the conductive fine powders are interposed. Effect tends to be insufficient.

The material of the roller member is not limited to an elastic foam, but may be ethylene-propylene-diene polyethylene (EPD).
M), urethane, butadiene acrylonitrile rubber (N
BR), silicone rubber, isoprene rubber, or the like, and a rubber material in which a conductive substance such as carbon black or metal oxide is dispersed for resistance adjustment, or foamed rubber material. It is also possible to adjust the resistance by using an ionic conductive material without dispersing the conductive material or in combination with the conductive material.

The roller member is disposed by being pressed against the image carrier as an image carrier with a predetermined pressing force against elasticity to form a charging nip portion which is a nip portion between the roller member and the image carrier. Let it. The width of the charging nip is not particularly limited, but is preferably 1 mm or more, more preferably 2 m, in order to obtain a stable and close adhesion between the roller member and the image carrier.
m or more is good.

The roller member may be provided with a release coating on the surface. Nylon resin, PVdF (polyvinylidene fluoride), PVdC
(Polyvinylidene chloride), fluorine acrylic resin and the like are applicable.

In the charging step of the present invention, it is preferable that the image carrier is charged by applying a voltage to the conductive brush member. As a brush member,
A fiber in which a conductive material is dispersed in generally used fibers and whose resistance is adjusted is used. 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, nickel, iron, aluminum, gold, a conductive metal such as silver or iron oxide, zinc oxide,
Examples thereof include oxides of conductive metals such as tin oxide, antimony oxide, and titanium oxide, and conductive powders 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.

Brush member (charging brush) as charging member
When using a fixed type, 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 10
~ 500μm), brush fiber length is 1 ~ 15m
m, brush density is 10,000 to 300,000 brushes per square inch (1.5 × 10 ^{7 to} 4.5 × 10 ⁸ per square meter)
) Are 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, it is also possible to bundle 50 fine fibers of 300 denier, such as 300 denier / 50 filament, and to implant hair as one fiber. However, in the present invention, the charging point of the direct injection charging is determined mainly depending on the density of the conductive fine powder in the vicinity of the charging nip between the charging member and the image carrier and the vicinity thereof. Therefore, the range of selection of the charging member is widened.

The resistance value of the charging brush is preferably 10 ³ Ω · cm to 10 ⁸ Ω · cm in order to obtain sufficient charging properties and leakage resistance, as in the case of the elastic conductive roller described above.
More preferably, the resistance is 10 ⁴ to 10 ⁷ Ω · cm.

As the material of the charging brush, conductive rayon fibers REC-B and REC-B manufactured by Unitika Ltd. were used.
C, REC-M1, REC-M10, and Toray Industries, Inc.
SA-7 manufactured by Nippon Sericulture Co., Ltd., Sanderon manufactured by Kanebo Co., Ltd., Bertron manufactured by Kaneray Co., Ltd., Cracarbo manufactured by Kuraray Co., Ltd.
There are products made of REC-
B, REC-C, REC-M1, REC-M10 are particularly preferred.

In addition, the fact that the charging member is flexible increases the chance that the conductive fine powder comes into contact with the image carrier in the nip portion between the charging member and the image carrier, thereby obtaining high contact properties. From the viewpoint of improving direct injection chargeability. That is, the charging member comes into close contact with the image carrier via the conductive fine powder, and the conductive fine powder present in the nip portion between the charging member and the image carrier rubs the image carrier surface without gaps. In the charging of the image carrier by the charging member, stable and safe direct injection charging without using a discharge phenomenon is dominant due to the presence of the charge promoting particles, and a high charging efficiency which cannot be obtained by conventional roller charging or the like is obtained. Thus, a potential substantially equal to the voltage applied to the charging member can be given to the image carrier.

In the charging step of the present invention, good charging properties can be obtained only by applying a DC bias to the charging bias applied to the charging member, but an alternating voltage (AC voltage) may be superimposed on the DC voltage.

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

In the charging step of the present invention, the DC voltage or a voltage obtained by superimposing an AC voltage having a peak-to-peak voltage of less than 2 × Vth (V) on the DC voltage when the discharge starting voltage in the DC application is Vth. Preferably, the process is a process of charging the image carrier by applying a voltage to a charging member. Further, in the charging step in the present invention, the DC voltage or a voltage obtained by superimposing an AC voltage having a peak-to-peak voltage less than Vth (V) on the DC voltage when a discharge starting voltage in DC application is Vth is applied to the charging member. It is more preferable to apply the voltage to charge the image carrier substantially without causing a discharge phenomenon in order to prevent generation of ozone and the like.

An example of preferable process conditions when a roller member is used as a charging member in the charging step of the present invention is as follows. The contact pressure of the roller member against the image carrier is 4.9 to 490 N / m (5 to 490 N / m). 500g / cm)
A DC voltage or a DC voltage with an AC voltage superimposed thereon is used. In the case of using a DC voltage superimposed on an AC voltage, an AC voltage = 0.5 to 5 kVpp, an AC frequency = 50 Hz to 5 kHz, and a DC voltage = ± 0.2 to ± 5
kV is preferred.

Next, the image carrier used in the image forming method of the present invention will be described. The image carrier used in the present invention may have a known structure having a conductive substrate and a photosensitive layer formed on the conductive substrate. The photosensitive layer is preferably formed of a plurality of layers having different functions selected from an undercoat layer, a charge generation layer, a charge transport layer, a charge injection layer, a protective layer, and the like.

In the image forming method of the present invention,
The volume resistance of the outermost surface layer of the body is 1 × 10 ⁹Ω · cm or more 1 ×
10¹⁴Ω · cm or less gives better chargeability
Is preferable. Charging method by direct injection of electric charge
In the case of, by reducing the resistance on the image carrier side,
Transfer of charges can be performed well. To do this,
The volume resistance value of the surface layer is 1 × 10¹⁴Ω · cm or less
Preferably, there is. On the other hand, an electrostatic latent image is used as an image carrier.
In order to maintain a certain time, the volume resistance of the outermost layer is required.
1 × 10⁹Ω · cm or more is preferred
New

Further, the image bearing member is an electrophotographic photosensitive member,
The volume resistivity of the outermost surface layer of the electrophotographic photosensitive member is 1 × 10 ⁹ Ω
・ Cm or more and 1 × 10 ¹⁴ Ω ・ cm or less
Even in an apparatus having a high process speed, a sufficient charging property can be provided, which is more preferable.

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

The organic photosensitive layer may be a single layer type in which the photosensitive layer contains a charge generating substance and a substance having charge transporting ability in the same layer, or a functional separation type photosensitive layer having a charge transporting layer and a charge generating layer. There may be. 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.

According to the image forming method of the present invention, charging can be performed more stably and uniformly by adjusting the surface resistance of the image carrier. In order to make charge injection more efficient or accelerated by adjusting the surface resistance of the image carrier, it is also preferable to provide a charge injection layer on the surface of the electrophotographic photosensitive member. The charge injection layer preferably has a form in which conductive fine particles are dispersed in a resin.

Examples of the mode of providing a charge injection layer include: (i) a case where a charge injection layer is provided on an inorganic photoreceptor such as selenium or amorphous silicon or a single-layer type organic photoreceptor; When a charge transport layer of a photoreceptor has a surface layer having a charge transport agent and a resin and also has a function as a charge injection layer (for example, the charge transport agent and the conductive particles are dispersed in a resin as the charge transport layer). Or when the charge transporting layer itself has a function as a charge injection layer depending on the charge transporting agent itself or its existence state) (iii) Further, when a charge injection layer is provided as the outermost surface layer on the function-separated type organic photoreceptor However, it is important that the volume resistance of the outermost surface layer is in a preferable range.

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

Among them, the outermost surface layer of the image carrier is preferably a resin layer in which conductive fine particles containing at least a metal oxide are dispersed, so that the surface resistance of the electrophotographic photosensitive member can be reduced more efficiently. In order to suppress the blur or flow of the latent image due to the diffusion of the latent image charge by enabling the transfer of electric charge and reducing the surface resistance while holding the electrostatic latent image as the image carrier Is preferred.

In the case of the conductive fine particle dispersion layer, it is necessary that the particle size of the particles is smaller than the wavelength of the incident light in order to prevent scattering of the incident light by the dispersed particles. Is preferably 0.5 μm or less.

The content of the conductive fine particles is preferably 2 to 90% by mass relative to the total weight of the outermost surface layer, and is preferably 5 to 70% by mass.
% Is more preferred. If less than 2% by mass,
If it is difficult to obtain a desired volume resistance value, and if it is more than 90% by mass, the film strength is reduced, the charge injection layer is easily scraped off, and the life of the photoconductor tends to be shortened. Also, when the amount of the conductive fine particles is large, the resistance is lowered, and an image defect is likely to occur due to the flow of the latent image potential.

The thickness of the outermost surface layer is preferably 0.1 to 10 μm, and 5 μm to obtain a sharp outline of the latent image.
The thickness is more preferably 1 μm or more from the viewpoint of the durability of the charge injection layer.

The binder of the charge injection layer can be the same as the binder of the lower layer. In this case, the coating surface of the lower layer (for example, the charge transport layer) is disturbed when the charge injection layer is coated. In such a case where the binders of the layers in contact with each other are the same, it is necessary to particularly select a method of forming the layers.

The method of measuring the volume resistivity of the outermost surface layer of the image carrier according to the present invention is based on the same composition as the outermost surface layer of the image carrier on a polyethylene terephthalate (PET) film having gold deposited on the surface. And a volume resistance measuring device (414 manufactured by Hewlett-Packard Company).
OB pA MATER), and a voltage of 100 V is applied in an environment of 23 ° C. and 65% for measurement.

Further, in the present invention, it is preferable to impart releasability to the surface of the image carrier, and the contact angle of water on the surface of the image carrier is preferably 85 degrees or more, and 90 degrees or more.
It is more preferable that the temperature is not less than the degree.

The means for imparting releasability to the surface layer of the image bearing member includes (1) using a resin having a low surface energy for the resin constituting the film, and (2) imparting water repellency and lipophilicity. (3) dispersing a material having high releasability selected from at least a fluorine-based resin, a silicone-based resin, and a polyolefin-based resin into a powder (lubricant fine particles), and the like. .

The means (1) can be achieved by introducing a fluorine-containing group, a silicone-containing group, etc. into the structure of the resin. As means (2), a surfactant or the like may be used as an additive. As means (3), use of a compound containing a fluorine atom, that is, a material such as polytetrafluoroethylene, polyvinylidene fluoride, or carbon fluoride may be mentioned.

By these means, the contact angle of water on the surface of the image bearing member can be 85 ° or more (preferably 90 ° or more), and the transferability of the toner and the durability of the photosensitive member can be further improved. . Among them, polytetrafluoroethylene is particularly preferable. In the present invention, among the above-mentioned means, the dispersion of the releasable powder such as the fluorine-containing resin in the outermost surface layer of (3) is suitable for imparting releasability to the surface of the image carrier. .

In order to incorporate these lubricant fine particles on the surface, a layer in which the particles are dispersed in a binder resin is provided on the outermost surface of the photoreceptor, or an organic photoreceptor originally composed mainly of resin is used. In this case, the particles may be dispersed in the uppermost layer without providing a new surface layer. Therefore, it is preferable that the image carrier is a photoconductor using a photoconductive substance in order to impart desired physical properties to the outermost surface layer of the image carrier.

The addition amount of the lubricant fine particles 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 magnetic toner and the durability of the image carrier is insufficient. It is not preferable because it tends to decrease.

According to the present invention, since the charging member contacts the image carrier to charge the image carrier, the generation of ozone is reduced as compared with a method such as corona discharge in which the charging member does not contact the image carrier. This is preferable in terms of a small number, but since the load on the surface of the image bearing member is large, the above-mentioned configuration has a remarkable improvement effect in terms of the life of the photoreceptor, and is one of preferable application forms.

Further, the present invention is effective when the surface of the photoreceptor is mainly composed of a polymer binder. For example, when a protective film mainly composed of resin is provided on an inorganic photoreceptor such as selenium or amorphous silicon, or as a charge transport layer of a function-separated organic image carrier, a surface layer made of a charge transport material and a resin is used. In some cases, a layer having the above-described releasability is further provided thereon as a protective layer.

FIG. 8 is a schematic diagram of a layer structure of a photoreceptor provided with a charge injection layer as a surface layer. That is, the photoreceptor is a general organic photoreceptor coated on a conductive substrate (aluminum substrate) 11 in the order of a conductive layer 12, a positive charge injection preventing layer 13, a charge generation layer 14, and a charge transport layer 15. The charge performance is improved by applying the charge injection layer 16 to the drum.

An important point of the charge injection layer 16 is that the volume resistivity of the surface layer is 1 × 10 ⁹ Ω · cm or more and 1 × 10 ¹⁴ Ω · c.
m or less. Even when the charge injection layer 16 is not provided as in the present configuration, for example, when the charge transport layer 15 is in the above-described resistance range, the same effect can be obtained. For example, even when an amorphous silicon photoreceptor having a surface layer having a volume resistance of about 10 ¹³ Ωcm is used, good chargeability can be similarly obtained.

One preferred embodiment of the image bearing member (photosensitive member) used in the present invention is described below. Examples of the conductive substrate include metals such as aluminum and stainless steel, plastics having a coating layer of an aluminum alloy, indium oxide-tin oxide alloy, etc., paper and plastic impregnated with conductive particles, and plastics having a conductive polymer. Cylindrical cylinders and films are used.

On these conductive substrates, the adhesion of the photosensitive layer is improved, the coating property is improved, the substrate is protected, the defect is coated on the substrate,
An undercoat layer may be provided for the purpose of improving the charge injection property from the substrate and protecting the photosensitive layer against electrical destruction. The undercoat layer is made of polyvinyl alcohol, poly-N-vinyl imidazole, polyethylene oxide, ethyl cellulose, methyl cellulose, nitrocellulose, ethylene-acrylic acid copolymer, polyvinyl butyral, phenol resin, casein, polyamide, copolymerized nylon, glue,
It is formed of a material such as gelatin, polyurethane, and aluminum oxide. The film pressure is usually 0.1 to 10 μm,
Preferably it is 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, acetic acid Vinyl resin and the like. 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 substance in a solvent together with a binder resin if necessary, and applying the solution. The film pressure is generally 5 to 40 μm.

Examples of the charge transporting substance include polycyclic aromatic compounds having a structure such as biphenylene / anthracene / pyrene / phenanthrene in the main chain or side chain; nitrogen-containing cyclic compounds such as indole / carbazole / oxadiazole / pyrazoline; Examples include hydrazone compounds, styryl compounds, selenium, selenium-tellurium, amorphous silicon, and cadmium sulfide.

The binder resin for dispersing these charge transporting substances includes polycarbonate resin, polyester resin, polymethacrylate, polystyrene resin, and the like.
Examples include resins such as acrylic resins and polyamide resins, and organic photoconductive polymers such as poly-N-vinylcarbazole and polyvinylanthracene.

A protective layer may be provided as a surface layer. As the resin of the protective layer, polyester, polycarbonate, acrylic resin, epoxy resin, phenol resin, or a curing agent of these resins or the like is used alone or in combination of two or more.

Also, conductive fine particles may be dispersed in the resin of the protective layer. Examples of the conductive fine particles include metals and metal oxides, and 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 in combination of two or more.

In general, when particles are dispersed in a protective layer,
It is necessary that the particle size of the particles is smaller than the wavelength of the incident light in order to prevent scattering of the incident light by the dispersed particles. It is preferably 0.5 μm or less. The content in the protective layer is 2 to 2 with respect to the total weight of the protective layer.
90 mass% is preferable, and 5-80 mass% is more preferable. The thickness of the protective layer is preferably from 0.1 to 10 μm,
~ 7 µm is more preferred. The application of the surface layer can be performed by spray coating, beam coating or penetration (dipping) coating of the resin dispersion. These layer thicknesses are measured by a high-frequency film thickness meter (for example, Permascope E111) manufactured by Helmut Fischer.

The image forming method of the present invention includes a latent image forming step of writing image information as an electrostatic latent image on a charged surface of an image carrier. The latent image forming step in the present invention is preferably a step of writing image information as an electrostatic latent image on a charged surface of an image carrier by image exposure. In the latent image forming step, a known latent image forming unit is used.

The latent image forming means for forming an electrostatic latent image is not limited to a laser scanning exposure means for forming a digital latent image, but may be other analog image exposure, LED or the like. Or a combination of a light emitting element such as a fluorescent lamp and a liquid crystal shutter or the like as long as an electrostatic latent image corresponding to image information can be formed.

Further, in the present invention, an image carrier such as an electrostatic recording dielectric can be used. In this case, after the dielectric surface is uniformly primary-charged to a predetermined polarity / potential, the static elimination needle is used. A latent image forming means for writing and forming a target electrostatic latent image by selectively removing charge by means of a charge removing means such as a head or an electron gun can be used.

The image forming method of the present invention includes a developing step of visualizing an electrostatic latent image as a toner image with a magnetic toner carried on a toner carrier. In the developing step in the present invention, a known developing unit is used. As such developing means, for example, a non-magnetic and conductive sleeve (toner carrier) having a magnetic field generating means fixed inside and a rotatably provided at an opening of the developing container is used as such a developing means. ), A layer thickness regulating member that regulates the layer thickness of the magnetic toner carried on the toner carrier, and a developing means for applying a voltage to the sleeve.

In the image forming method of the present invention, the developing step also serves as a cleaning step for recovering the magnetic toner remaining on the image carrier after transferring the toner image onto the recording medium. It is preferable to use an image forming method called a method or a cleanerless image forming method.

The developing step in the present invention is a step of forming a toner layer of 5 to 30 g / m ^{2 on} the toner carrier, transferring the magnetic toner from the toner layer to the image carrier, and developing the electrostatic latent image. Is preferred. If the toner amount on the toner carrier is less than 5 g / m ^2, it is difficult to obtain a sufficient image density, and the toner layer tends to be uneven due to excessive charging of the magnetic toner. If the amount of toner on the toner carrier is more than 30 g / m ² , toner scattering is likely to occur.

In the developing step of the present invention, the gap between the image carrier and the toner carrier is preferably 100 to 1000 μm. If the distance between the toner carrier and the image carrier is smaller than 100 μm, the change in the development characteristics of the magnetic toner with respect to the fluctuation of the distance increases,
In some cases, it may be difficult to mass-produce an image forming apparatus satisfying stable image quality. If the separation distance of the toner carrier from the image carrier is greater than 1000 μm, the ability of the magnetic toner to follow the latent image on the image carrier is reduced, so that image quality such as resolution and image density is reduced. May be invited. Preferably, it is 120 to 500 μm.

In the developing step in the present invention, the gap between the image carrier and the toner carrier, that is, the closest distance (S
It is preferable to form a toner layer having a smaller thickness on the toner carrier, and transfer the magnetic toner from the toner layer to the image carrier to develop an electrostatic latent image. That is, in the developing step of the present invention, the closest gap between the photoconductor and the toner carrier is set to be wider than the thickness of the toner layer on the toner carrier by the layer pressure regulating member that regulates the magnetic toner on the toner carrier. Is particularly preferable from the viewpoint of uniformly charging the magnetic toner.

Further, by applying the non-contact type developing method of visualizing the electrostatic latent image of the image carrier as a toner image by making the toner layer non-contact with the image carrier as described above, Even if conductive fine powder having a low value is added to the magnetic toner, the occurrence of development fog due to injection of a developing bias into the image carrier is suppressed, and a good image can be obtained.

In the developing step in the image forming method of the present invention, the electrostatic latent image is formed while the toner carrier carrying the magnetic toner and transporting it to the developing section for the image carrier has a speed difference with respect to the image carrier. In the developing step, the toner particles and the conductive fine powder are sufficiently supplied from the toner carrier to the image carrier, so that a good image can be obtained.

In this case, the surface of the toner carrier that carries the magnetic toner may move in the same direction as 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. 10
If it is less than 0%, the image quality tends to decrease. The higher the moving speed ratio, the greater the amount of magnetic toner supplied to the development site, the more frequently the magnetic toner is attached to and detached from the latent image, and unnecessary portions are scraped off and given to necessary portions. By repeating, an image faithful to the latent image tends to be obtained. Specifically, the moving speed of the surface of the toner carrier is 1.05 to 1.0 times the moving speed of the surface of the image carrier.
Preferably, the speed is 3.0 times.

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 for development, and the applied developing bias may be obtained by superimposing an alternating voltage (AC voltage) on a DC voltage. Good. As the waveform of the alternating voltage, a sine wave, a rectangular wave, a triangular wave, or the like can be used as appropriate. Alternatively, a pulse wave formed by periodically turning on / off a DC power supply may be used. As described above, a bias whose voltage value periodically changes can be used as the waveform of the alternating voltage.

In the case where the image forming method of the present invention is a developing / cleaning image forming method, in the developing step of the present invention, at least an alternating voltage is applied between the toner carrying member carrying the magnetic toner and the image carrying member. This is a step of developing the electrostatic latent image on the image carrier with magnetic toner by applying a bias, and the alternating electric field is 3 × 10
^{6 ~10 7} V / m, it is preferable that the frequency 100～5000Hz. If the electric field intensity due to the developing bias applied between the toner carrier and the image carrier is smaller than 3 × 10 ⁶ V / m, the recoverability of the transfer residual toner to the developing device is reduced, and the fog due to defective recovery is reduced. Tends to occur. Further, since the developing power is small, an image having a low image density tends to be formed.

On the other hand, when the electric field strength
^If it is higher than ⁷ V / m, the developing power is too large, and the resolution is reduced due to the collapse of fine lines, the image quality is easily reduced due to the increase of fog, and the image bias is easily generated due to the leakage of the developing bias to the image carrier. Become.

The frequency of the AC component of the developing bias applied between the toner carrier and the image carrier is 100 Hz.
If it is smaller than this, the frequency of attaching and detaching the magnetic toner to and from the latent image decreases, and the recoverability of the transfer residual toner to the developing device tends to decrease, and the image quality tends to decrease. Development bias AC
If the frequency of the component is greater than 5000 Hz, the amount of magnetic toner that can follow the change in the electric field decreases, so that the recoverability of the transfer residual toner decreases and the developability tends to decrease.

Even when there is a high potential difference between the toner carrier and the image carrier due to application of an alternating voltage as a developing bias or the like, charge injection into the image carrier by the developing unit does not occur. The conductive fine powder added to the toner is easily transferred to the image carrier side evenly, and the conductive fine powder is uniformly applied to the image carrier, and a uniform contact is made in the charging section to obtain good chargeability. I can do it.

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 toner carrier may have a conductive cylinder formed of a resin composition having sufficient mechanical strength and conductivity, or a conductive rubber roller may be used. Also,
The toner carrier 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 JIS center line average roughness (Ra).
It is preferably in the range of 3.5 μm. Ra is 0.2
If it is less than μm, the charge amount on the toner carrier increases, and developability tends to be insufficient. Ra is 3.5 μm
If it exceeds, the toner coat layer on the toner carrier becomes uneven, and the density tends to be uneven on the image. The Ra of the toner carrier is more preferably in the range of 0.5 to 3.0 μm.

In the present invention, the surface roughness Ra of the toner carrier is determined based on JIS surface roughness “JIS B 0601” by using a surface roughness measuring device (for example, Surfcoder SE-30).
H, manufactured by Kosaka Laboratory Co., Ltd.). Specifically, a portion of 2.5 mm as a measurement length a is extracted from the roughness curve in the direction of its center line, the center line of the extracted portion is the X axis, the direction of the vertical magnification is the Y axis, and the roughness curve is When y = f (x), the value obtained by the following equation is expressed in micrometer (μm).

[0355]

(Equation 5)

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

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

The conductive fine particles contained in the resin material 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.

The conductive fine particles contained in the resin material are as follows:
It is preferable to use 3 to 20 parts by mass per 10 parts by mass of the resin component. When 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 sleeve in which the conductive fine powder contained in the resin material is dispersed is 10%.
^{-6 ~10 6 Ω} · cm is preferable.

The resin material forming the resin layer is, for example, styrene resin, vinyl resin, polyether sulfone resin, polycarbonate resin, polyphenylene oxide resin, polyamide resin, fluororesin, cellulose resin, acrylic resin. Thermoplastic resins such as epoxy resins, polyester resins, alkyd resins, phenol resins, melamine resins, polyurethane resins, urea resins, silicone resins, and polyimide resins can be used.

Among them, those having releasability such as silicone resin and fluorine resin, or excellent in mechanical properties such as polyether sulfone, polycarbonate, polyphenylene oxide, polyamide, phenol resin, polyester, polyurethane, and styrene resin. Are more preferable as the resin material. Particularly, a phenol resin is preferable.

In the present invention, the fact that the layer thickness regulating member that regulates the magnetic toner on the toner carrier is in contact with the toner carrier via the magnetic toner is regulated by the temperature of the magnetic toner. It is particularly preferable from the viewpoint of making the device less susceptible to the humidity environment and obtaining uniform charging with less toner scattering. An example of such a layer thickness regulating member is an elastic blade formed of an elastic material such as rubber.

The image forming method of the present invention includes a transfer step of transferring a toner image on an image carrier to a recording medium. The transfer step in the present invention is preferably a contact transfer step in which the transfer member contacts the recording medium to the image carrier at the time of transfer, and transfers the toner image on the image carrier to the recording medium. 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 can be obtained by re-transferring from the intermediate transfer member to a transfer material such as paper.

In the contact transfer step, the contact pressure between the image carrier and the transfer member was set to a linear pressure of 2.9 N / m (3 g / c
m) or more, and more preferably 19.
6 N / m (20 g / cm) or more. If the linear pressure as the contact pressure is less than 2.9 N / m (3 g / cm), it is not preferable because the transfer of the transfer material and the occurrence of transfer failure tend to occur.

As the transfer means in the contact transfer step, a known device 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 a core metal 34a and a conductive elastic layer 34b, and the conductive elastic layer is made of a material such as urethane or EPDM in which a conductive material such as carbon is dispersed.
0 ⁶ 10 ¹⁰ are made of Ωcm about elastic body, a transfer bias is applied by the transfer bias power source 35.

In the image forming method of the present invention, the conductive fine powder contained in the magnetic toner adheres to the image carrier in the developing step,
It is more preferable that the toner remains on the image carrier even after the transfer step and is present at least in the charging member and at least the nip portion of the image carrier and the vicinity thereof in the charging step.

The image forming method of the present invention is particularly effective when a contact transfer method is used for an image bearing member whose surface is made of 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, examples of the surface material of the photoreceptor used include silicone resin, vinylidene chloride, ethylene-vinyl chloride, styrene-acrylonitrile, and styrene-methyl. Examples include methacrylate, styrene, polyethylene terephthalate, and polycarbonate, but are not limited thereto, and other monomers or copolymers and blends of the above-mentioned binder resins may be used.

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 image carrier having a diameter of 50 mm or less. That is, in the case of a small-diameter photosensitive member, the curvature for the same linear pressure is large, and the concentration of pressure in the contact portion is likely to occur. Although the same phenomenon is considered to occur in the belt-shaped image carrier, the present invention has a curvature radius of 25 mm at the transfer portion.
The present invention is also effective for the following image forming apparatuses.

Next, an example of an image forming method for realizing the image forming method of the present invention will be specifically described with reference to the drawings. FIG.
In the figure, reference numeral 100 denotes a drum-shaped photosensitive member as an image carrier, around which a charging roller 117 as a charging member, a developing device 140, a transfer roller 114 as a transfer member, a cleaner 116, a register roller 124, and the like are provided. I have. Then, the photoconductor 100 is charged to −700 V by the charging roller 117. (The applied voltage is AC voltage-2.
0 kVpp, DC voltage -700 Vdc).
Exposure is performed by irradiating zero. The electrostatic latent image on the photoconductor 100 is developed with the magnetic toner by the developing device 140, and is transferred onto the transfer material by the transfer roller 114 that is in contact with the photoconductor via the transfer material. The transfer material bearing the toner image is carried 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 photoconductor is cleaned by the cleaner 116.

As shown in FIG. 2, the developing device 140
A cylindrical toner carrier 102 (hereinafter referred to as a developing sleeve) made of a non-magnetic metal such as aluminum or stainless steel is provided in the vicinity of the photoconductor 100, and a gap between the photoconductor 100 and the developing sleeve 102 is not shown. It is maintained at about 300 μm by a photosensitive member gap holding member or the like. Inside the developing sleeve, a magnet roller 104 is fixed and disposed concentrically with the developing sleeve 102. However, the developing sleeve 102 is rotatable. Magnet roller 10
4, a plurality of magnetic poles are provided as shown, S1 affects development, N1 regulates toner coat amount, S2 influences toner take-in / conveyance, and N2 affects toner blow-out prevention.

As a member for regulating the amount of magnetic toner adhered and conveyed to the developing sleeve 102, the elastic blade 10
3, the developing sleeve 102 of the elastic blade 103
The amount of toner conveyed to the development area is controlled by the contact pressure with respect to. In the developing area, a DC and AC developing bias is applied between the photosensitive member 100 and the developing sleeve 102, and the toner on the developing sleeve is charged to the photosensitive member 1 in accordance with the electrostatic latent image.
It flies above 00 and becomes a visible image.

As described above, the image forming method of the present invention can suitably employ the developing and cleaning image forming method. Hereinafter, an example of an image forming apparatus for realizing the developing and cleaning image forming method according to the present invention will be described.

FIG. 5 is a schematic structural diagram of an example of the image forming apparatus according to the present invention. The image forming apparatus according to the present embodiment includes:
It is a laser printer (recording device) of a developing and cleaning process (cleanerless system) using a transfer type electrophotographic process. It has a process cartridge from which a cleaning unit having a cleaning member such as a cleaning blade has been removed, uses a magnetic one-component toner (the above-described magnetic toner) as a toner, and forms a toner layer on a toner carrier and an image carrier. It is an example of non-contact development arranged so as to be non-contact.

(1) Overall Schematic Configuration of Printer According to the Embodiment Reference numeral 21 denotes a rotating drum type OPC photosensitive member as an image carrier, which is driven to rotate in the clockwise direction of the arrow at a peripheral speed (process speed) of 94 mm / sec. Is done. Reference numeral 22 denotes a charging roller as a charging member (roller member). The charging roller 22 is disposed in pressure contact with the photosensitive member 21 with a predetermined pressing force against elasticity. “n” denotes a charging contact portion that is a contact portion between the photoconductor 21 and the charging roller 22.

In this embodiment, the charging roller 22 is rotationally driven at a peripheral speed ratio of 100% in a facing direction (a direction opposite to the moving direction of the photosensitive member surface) at a charging contact portion n which is a contact surface with the photosensitive member 21. Have been. That is, the surface of the charging roller 2 as a charging member has a speed difference with respect to the surface of the photoconductor 21. The conductive fine powder 3 was applied to the surface of the charging roller 22 so that the applied amount was approximately 1 × 10 ⁴ / mm ² .

Further, a DC voltage of -700 V was applied as a charging bias from a charging bias applying power source to the core metal 22a of the charging roller 2. In the present 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.

Reference numeral 23 denotes a laser beam scanner (exposure device) including a laser diode, a polygon mirror, and the like.
This laser beam scanner outputs a laser light intensity-modulated according to a time-series electric digital pixel signal of target image information, and scans and uniformly exposes the uniformly charged surface of the photoconductor 21 with the laser light. By this scanning exposure L, an electrostatic latent image corresponding to the target image information is formed on the surface of the rotating photoconductor 21.

Numeral 24 is a developing device. The electrostatic latent image on the surface of the photoconductor 21 is developed as a toner image by this developing device. The developing device 24 of the present embodiment is a non-contact reversal developing device using the negatively chargeable magnetic one-component insulating toner B of the present invention as a magnetic toner. Toner B has a conductive fine powder added externally.

The gap between the photosensitive member 21 and the developing sleeve 24a was 290 μm. The toner carrier 24a has a layer thickness of about 7 μm and a JIS center line average roughness (R
a) A resin layer of 1.0 μm was blasted on the surface and had a diameter of 1
A developing sleeve formed on a 6 mm aluminum cylinder was used. The sleeve includes a magnet roll having a developing magnetic pole of 90 mT (900 gauss).
1.0mm thickness, 1.5m free length as toner regulating member
m of a urethane blade of 29.4 N / m (30 g / c
m). Phenol resin 100 parts Graphite (particle size: about 7 μm) 90 parts Carbon black 10 parts

Further, the photosensitive member 21 is rotated at a peripheral speed of 120% of the peripheral speed of the photosensitive member 21 in a forward direction with respect to the rotation direction of the photosensitive member 21 in a developing portion a (developing area) which is a portion facing the photosensitive member 21. The developing sleeve 24a is coated with a thin layer of magnetic toner by an elastic blade 24c. 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 amount of toner coated on the developing sleeve 24a was 15 g / m ² . The magnetic toner coated on the developing sleeve 24a is
Is conveyed to the developing section a, which is the opposing section of the photoconductor 21 and the developing sleeve 24a.

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 160.
0 Hz, peak-to-peak voltage 1500 V (electric field intensity 5 × 10 ⁶
V / m), and one-component jumping development was performed between the developing sleeve 24a and the photosensitive member 21 using a superimposed rectangular AC voltage.

Numeral 25 denotes a medium-resistance transfer roller as a contact transfer means, which applies 98 N / m (100 g /
cm) to form a transfer nip b. A transfer material P as a recording medium is supplied to the transfer nip b from a paper supply unit (not shown) at a predetermined timing, 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 embodiment, the roller resistance value is 5 × 10 ⁸
The transfer was performed by applying a DC voltage of +3000 V using a Ωcm. 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 is sequentially transferred by electrostatic force and pressing force. It is transferred to the surface side of P.

Reference numeral 26 denotes a fixing device such as a heat fixing system. 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 the present embodiment, the cleaning unit is removed, and the transfer residual toner remaining on the surface of the photosensitive member 21 after the transfer of the toner image onto the transfer material P is not removed by the cleaner. With rotation, it reaches the developing unit a via the charging unit n, and is developed and cleaned (collected) in the developing device 24.

Reference numeral 27 denotes a process cartridge which is detachable from the printer main body. The printer according to the present embodiment includes a photoconductor 21, a charging roller 22, and a developing device 24.
The two process devices are collectively configured as a process cartridge that is detachable from the printer body. The combination of the process devices to be formed into the process cartridge is not limited to the above, and is optional.

Reference numeral 28 denotes a process cartridge attaching / detaching guide.
It is a holding member.

(2) Behavior of the conductive fine powder in the present embodiment The conductive fine powder m mixed into the magnetic toner t of the developing device 24 is the toner of the electrostatic latent image on the photoconductor 21 side by the developing device 24. During development, an appropriate amount moves to the photoconductor 21 side together with the toner. The toner image on the photoreceptor 21 is attracted to the transfer material P, which is a recording medium, by the influence of a transfer bias in the transfer portion b and is positively transferred, but the conductive fine powder m on the photoreceptor 21 is conductive. As a result, the transfer material P is not positively transferred to the transfer material P side, but remains substantially adhered and held on the photoconductor 21.

In the present invention, since the image forming apparatus does not have an independent cleaning mechanism, the transfer residual toner remaining on the surface of the photoreceptor 21 after the transfer and the residual conductive fine powder m are transferred to the photoreceptor 21. Then, the photosensitive member 21 is carried as it is to a charging portion n which is a contact portion of the charging roller 22 serving as a charging member, and adheres to or mixes with the charging roller 22. Therefore, the photosensitive member 21 and the charging roller 22
In the state where the conductive fine powder m is present in the nip portion n, the photosensitive member 21 is directly charged.

[0392] Due to the presence of the conductive fine powder m, even when the toner adheres to or mixes with the charging roller 22, the fine contact property and contact resistance of the charging roller 22 to the photosensitive member 21 can be maintained. Photoconductor 21 by 22
For direct injection charging. That is, the charging roller 22 is densely packed with the photosensitive member 21 via the conductive fine powder m.
And the conductive fine powder m present on the mutual contact surface between the charging roller 22 and the photoconductor 21 rubs the surface of the photoconductor 21 without gaps.
The stable fine charging that does not use a discharge phenomenon is dominant due to the presence of the conductive fine powder m, and a high charging efficiency that cannot be obtained by conventional roller charging or the like is obtained. A potential substantially equal to the applied voltage can be applied 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 to the photosensitive member 2.
1 and is moved to the developing unit with the movement of the surface of the photoreceptor 21, and is developed and cleaned (recovered) by the developing unit.
Is done.

In the development and cleaning, the photosensitive member 2 is transferred after the transfer.
The magnetic toner remaining on 1 is developed during a subsequent image forming process, that is, the photosensitive member is subsequently charged and exposed to form a latent image, and at the time of developing the latent image, the fogging bias of the developing device, that is, Fogging potential difference Vbac, which is the potential difference between the DC voltage applied to the developing device and the surface potential of the photoconductor.
k. In the case of reversal development as in the printer of the present embodiment, the development and cleaning is performed by applying an electric field for collecting the toner from the dark portion potential of the photoconductor to the developing sleeve by the developing bias and a magnetic field from the developing sleeve to the bright portion potential of the photoconductor. This is done by the action of an electric field that causes toner to adhere.

Also, by operating the image forming apparatus,
The conductive fine powder m mixed in the magnetic toner t of the developing device 24 moves to the surface of the photoreceptor 21 in the developing unit a, is carried to the charging unit n via the transfer unit b by the movement of the image bearing surface, and is charged. Since new particles m continue to be supplied to the portion n sequentially, even if the conductive fine powder m decreases in the charging portion n due to falling off or the like and the particles m deteriorate, the chargeability may be reduced. Thus, 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 charging member, and the low voltage is applied irrespective of the contamination of the charging roller 22 by the transfer residual toner. Ozone-less direct injection charging with voltage can be stably maintained for a long time, uniform charging properties can be provided, and there is no obstacle due to ozone products, failure due to charging failure, etc., simple configuration, low cost An image forming apparatus can be obtained.

As described above, since the conductive fine powder m does not impair the chargeability, the electric resistance value of the conductive fine powder m is 1 × 10
It must be ⁹ Ω · cm or less. Therefore, the developing unit a
In the case of using a contact developing device in which the magnetic toner comes into direct contact with the photoconductor 21 in (2), charge is injected into the photoconductor 21 by the developing bias through the conductive fine powder m in the magnetic toner, and image fogging occurs. .

However, in this embodiment, since the developing device is a non-contact type developing device, the developing bias is not injected into the photosensitive member 21 and a good image can be obtained.
In addition, since no charge is injected into the photoconductor 21 in the developing section a, a high potential difference can be provided between the developing sleeve 24a and the photoconductor 21 such as an AC bias, and the conductive fine powder m can be evenly distributed. The conductive fine powder m is easily applied to the surface of the photoreceptor 21 and is uniformly contacted by the charging unit, so that a good charging property can be obtained and a good image can be obtained. .

The conductive fine powder m is interposed on the contact surface n between the charging roller 22 and the photoreceptor 21, and the lubricating effect (friction reducing effect) of the conductive fine powder m causes the charging roller 22 and the photoreceptor 21 to contact each other. It is possible to easily and effectively provide a speed difference between them. Charging roller 22 and photoconductor 21
And a speed difference between the charging roller 22
Conductive fine powder m on the mutual contact surface n between
Greatly increases the chance of contact with the photoreceptor 21, high contact properties can be obtained, and good direct injection charging is possible.

In the present embodiment, the charging roller 22 is driven to rotate, and the rotating direction thereof is configured to rotate in the opposite direction to the moving direction of the surface of the photosensitive member 21. An effect of temporarily collecting the transfer residual toner on the charging roller 21 to the charging roller 22 and leveling the toner is obtained. That is, by directly separating the transfer residual toner on the photoreceptor 21 by rotation in the reverse direction and performing charging, direct injection charging can be performed with superiority.

Further, in the present embodiment, a suitable amount of conductive fine powder m is interposed in the charging contact portion n between the photosensitive member 21 as the image carrier and the charging roller 22 as the charging member, so that the particles are lubricated. The effect reduces friction between the charging roller 22 and the photoconductor 21, and the charging roller 22 can be easily driven to rotate with a speed difference between the photoconductor 21. That is, the driving torque is reduced, and the surface of the charging roller 22 and the surface of the photoconductor 21 can be prevented from being scraped or damaged. Further, sufficient charging performance can be obtained by increasing the contact chance by the particles. Further, there is no adverse effect on image formation due to the conductive fine powder falling off the charging roller 22.

[0402]

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

(Production Example 1 of Surface-treated Magnetic Powder) An aqueous solution containing ferrous hydroxide was prepared by mixing 1.0 to 1.1 equivalents of a caustic soda solution with respect to iron ions in an aqueous ferrous sulfate solution. Was prepared. Air was blown in while maintaining the pH of the aqueous solution at around 9, and an oxidation reaction was performed at 80 to 90 ° C. to prepare a slurry liquid for generating seed crystals. Next, the initial amount of alkali (sodium component of caustic soda) is added to this slurry liquid.
After adding an aqueous solution of ferrous sulfate so as to be 0.9 to 1.2 equivalents, the slurry solution is maintained at pH 8, and the oxidation reaction is promoted while blowing air thereinto. The magnetic iron oxide particles generated after the oxidation reaction Was washed, filtered and once taken out. At this time, a small amount of a water-containing sample was collected and the water content was measured. Next, after re-dispersing this water-containing sample in another aqueous medium without drying, the pH of the re-dispersed liquid was adjusted to about 6,
While sufficiently stirring, the silane coupling agent (nC ₁₀ H ₂₁
1.0 parts by mass of Si (OCH ₃ ) ₃ ) was added to the magnetic iron oxide (the amount of the magnetic iron oxide was calculated as a value obtained by subtracting the water content from the water-containing sample), and a coupling treatment was performed.
The produced hydrophobic iron oxide particles were washed, filtered, and dried by a conventional method, and then slightly aggregated particles were crushed to obtain surface-treated magnetic powder 1.

(Production Example 1 of Magnetic Powder) The oxidation reaction was advanced in the same manner as in Production Example 1 of the surface-treated magnetic powder, and the magnetic iron oxide particles generated after the oxidation reaction were washed, filtered, and then subjected to the surface treatment. The dried and agglomerated particles are crushed to obtain a magnetic powder 1
I got

(Production Example 2 of Surface-Treated Magnetic Powder) The magnetic powder 1 obtained in Production Example 1 of the magnetic powder was redispersed in another aqueous medium, and the pH of the redispersed liquid was reduced to about 6 and stirring the silane coupling agent (n-C ₁₀ H ₂₁ Si
(OCH ₃ ) ₃ ) was added to the magnetic iron oxide in an amount of 1.0 part by mass to perform a coupling treatment. The resulting hydrophobic iron oxide particles were washed, filtered, and dried by a conventional method, and then the aggregated particles were crushed to obtain surface-treated magnetic powder 2.

(Production Example 3 of Surface-treated Magnetic Powder) Surface-treated magnetic powder was prepared in the same manner as in Production Example 1 of surface-treated magnetic powder except that the treatment amount of the silane coupling agent was changed to 0.04 parts by mass. Body 3 was obtained.

(Conductive fine powder 1) 3.7 μm in volume average particle size
m, 6.6% by volume is 0.5 μm or less in the particle size distribution,
5% or more of fine particle zinc oxide of 8% by number (resistance is 80Ω
A product obtained by granulating primary particles of zinc oxide having a primary particle diameter of 0.1 to 0.3 μm in cm and white (white) is referred to as conductive fine powder 1. This conductive fine powder 1 was observed at a magnification of 3000 and 30,000 times with a scanning electron microscope.
0.1-0.3 μm zinc oxide primary particles and 1-10 μm
Of aggregates. According to the exposure light wavelength of 740 nm of the laser beam scanner used for image exposure in the image forming apparatus of Example 1, the transmittance in this wavelength range was measured using a light source having a wavelength of 740 nm by X-Rite 31.
When measured using a 0T 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, obtained by classifying the conductive fine powder 1 by wind power, is 4.1 vol% in 0.5 μm or less in particle size distribution, and 1 in 5 μm or more. The conductive fine powder 2 is made up of a few percent of zinc oxide fine particles (resistance: 440 Ω · cm, transmittance: 35%). When the conductive fine powder 2 was observed with a scanning electron microscope,
Although it was composed of 0.3 μm zinc oxide primary particles and 1 to 5 μm aggregates, the primary particles were reduced as compared with the conductive fine powder 1.

(Conductive Fine Powder 3) A volume average particle diameter of 1.5 μm obtained by classifying the conductive fine powder 1 by wind power is 35% by volume when 0.5 μm or less in the particle size distribution is 0% when 5 μm or more.
The conductive fine powder 3 is composed of a few percent of zinc oxide fine particles (resistance 1500 Ω · cm, transmittance 35%). Observation of this conductive fine powder 3 with a scanning electron microscope showed that
It consisted of zinc oxide primary particles of 0.3 μm and aggregates of 1 to 4 μm, but the primary particles increased as compared with the conductive fine powder 2.

(Conductive fine powder 4) Volume average particle diameter 0.3 μm
m, 80% by volume of 0.5 μm or less in particle size distribution, 5
Fine particle zinc oxide with 0% by number or more with a resistance of 100 Ω
Cm, the primary particle diameter is 0.1 to 0.3 μm, white, the transmittance is 35%, and the purity is 99% or more).
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, was subjected to air classification to remove coarse particles, then dispersed in an aqueous system and filtered repeatedly. By removing the fine particles by doing
Volume average particle size 3.2 μm, 0.5 μm in particle size distribution
Gray-white conductive particles having 0.4% by volume in the following and 5% or more in 1% by number were obtained. This is referred to as conductive fine powder 5. Table 1 below shows typical physical property values of the conductive fine powders 1 to 5.

[0412]

[Table 1]

(Production Example 1 of Toner) Ion-exchanged water 709
0.1M Na in g_ThreePO_FourAdd 451 g of aqueous solution and add
After warming to 1.0 ° C._TwoAqueous solution 67.7
g gradually added to Ca_Three(PO_Four)_TwoAqueous media containing
Obtained. Styrene 80 parts N-butyl acrylate 20 parts Unsaturated polyester resin 2 parts Saturated polyester resin 3 parts Negative charge control agent (monoazo dye-based Fe compound) 1 part Surface-treated magnetic powder 1 90 parts Attritor (Mitsui) Miike Kakoki Co., Ltd.)
And uniformly mixed. Bring the monomer composition to 60 ° C
It is heated, and there is a beauty treatment centered on behenyl behenate.
Luwax (maximum endothermic peak in DSC 72
° C, solubility test ○) 5 parts and polyethylene wax (DS
Maximum value of endothermic peak at C 89 ° C, solubility test
×) 5 parts were added, mixed and dissolved, and the polymerization initiator 2, 2 ′ was added thereto.
-Azobis (2,4-dimethylvaleronitrile) [t1 /
2 = 140 minutes, at 60 ° C]. The water
The above polymerizable monomer system was charged into a system medium,_Two
TK homomixer under special atmosphere
(15) at 10,000 rpm for 15 minutes.
Granulated. Then, at 60 ° C for 6 hours while stirring with paddle stirring blades.
Allowed to react for hours. Thereafter, the liquid temperature was set to 80 ° C., and the mixture was further stirred for 4 hours.
Stirring was continued. After completion of the reaction, distillation was conducted at 80 ° C. for another 2 hours.
Then, the suspension was cooled and hydrochloric acid was added to add Ca _Three(P
O_Four)_TwoIs dissolved, filtered, washed with water and dried to obtain a weight average particle size.
6.9 μm toner particles were obtained. 1k of this toner particle
Electron microscope (FE-SEM, manufactured by Hitachi: S-8)
00) In observation, no magnetic powder was present on the surface, and
Was not recognized. 100 parts of the toner particles and the primary
Surface treated with hexamethyldisilazane on silica with a particle size of 8nm
After treatment, treatment with silicone oil, BE after treatment
T value is 140m^Two/ G of hydrophobic silica fine powder of 1.2 parts / g
3, 2.0 parts of the conductive fine powder was mixed with a Henschel mixer (Mitsui
The mixture was mixed with Miike Kakoki Co., Ltd. to prepare toner A.
Tables 2 and 3 show the formulation and physical properties of Toner A.

(Toner Production Example 2) The weight average particle diameter was the same as in Toner Production Example 1 except that the magnetic powder was changed to the surface-treated magnetic powder 3 in the formulation of Toner Production Example 1. 6.6 μm toner particles were obtained, and the hydrophobic silica fine powder and the conductive fine powder 3 were mixed to prepare a toner B. Tables 2 and 3 show the formulation and physical properties of Toner B. Note that toner B
No electron microscopic observation revealed that the magnetic powder was exposed.

(Toner Production Example 3) In the formulation of Toner Production Example 1, the magnetic powder was removed, the amounts of the aqueous Na ₃ PO ₄ solution and the aqueous CaCl ₂ solution were changed, and the weight average particle diameter was reduced to 0.1. 5 μm toner particles (laser diffraction type particle size distribution meter
LS-230). Using 5 parts of the toner particles and 100 parts of the toner particles obtained in Production Example 1 of the toner, using an impact type surface treatment apparatus (processing temperature 60 ° C., rotating processing blade peripheral speed 90 m / sec.), Magnetic toner particles Spherical toner particles having a weight average particle size of 8.1 μm, on which non-magnetic toner particles were fixed and formed into a film, were obtained. The spherical toner particles obtained, 2.0 parts of the hydrophobic silica fine powder used in Production Example 1 of the toner and 3, 2.0 parts of the conductive fine powder were mixed with a Henschel mixer (Mitsui Miike Kakoki Co., Ltd.). Thus, a toner C was prepared. Tables 2 and 3 show the formulation and physical properties of Toner C. The electron microscopic observation of the toner C did not reveal the magnetic powder.

(Toner Production Example 4) In the same manner as in Toner Production Example 1, except that the magnetic powder was changed to the surface-treated magnetic powder 2 in the formulation of Toner Production Example 1, Toner D was prepared by mixing 6.6 μm toner particles and mixing hydrophobic silica fine powder and conductive fine powder. Tables 2 and 3 show the formulation and physical properties of Toner D. In addition, even when the toner D was observed with an electron microscope, no exposure of the magnetic powder was observed.

(Toner Production Example 5) In the same manner as in Toner Production Example 1, except that the formulation amounts of the ester wax and the polyethylene wax were changed to 0.2 parts in the formulation of the toner production example 1, respectively. Toner particles having a weight average particle diameter of 6.2 μm were obtained, and a fine powder of hydrophobic silica and a fine conductive powder were mixed to prepare a toner E. Tables 2 and 3 show the formulation and physical properties of Toner E. The electron microscopic observation of the toner E did not reveal the magnetic powder.

(Toner Production Example 6) In the same manner as in the toner 1 of the magnetic toner, except that the used amount of the ester wax was 51 parts in Production Example 1 of the toner, the weight average particle diameter was 8.
0 μm toner particles were obtained, and a hydrophobic silica fine powder and a conductive fine powder were mixed to prepare a toner F. Tables 2 and 3 show the formulation and physical properties of Toner F. The electron microscopic observation of the toner F did not reveal the magnetic powder.

(Toner Production Example 7) The weight average particle diameter was the same as in Toner Production Example 1 except that the formulation amount of the ester wax was changed to 0.2 part in the formulation of Toner Production Example 1. 6.2 μm toner particles were obtained, and a hydrophobic silica fine powder and a conductive fine powder were mixed to prepare a toner G. Tables 2 and 3 show the formulation and physical properties of Toner G. Note that the toner G
No electron microscopic observation revealed that the magnetic powder was exposed.

(Toner Production Example 8) The toner production example 1 was the same as the toner production example 1 except that the formulation amounts of the ester wax and the polyethylene wax were changed to 15 parts and 0.1 part, respectively. Similarly, the weight average particle size is 7.8.
μm toner particles were obtained, and a hydrophobic silica fine powder and a conductive fine powder were mixed to prepare a toner H. Tables 2 and 3 show the formulation and physical properties of Toner H. The electron microscopic observation of the toner H did not reveal any magnetic powder.

(Toner Production Example 9) In the formulation of Toner Production Example 1, all except that the ester wax was changed to 6 parts of montan wax (maximum endothermic peak in DSC at 66 ° C., solubility test ○). In the same manner as in Toner Production Example 1, toner particles having a weight average particle size of 8.7 μm were obtained, and a hydrophobic silica fine powder and a conductive fine powder were mixed to prepare toner I. Tables 2 and 3 show the formulation and physical properties of Toner I.
In addition, even when the toner I was observed with an electron microscope, no exposure of the magnetic powder was observed.

(Production Example 10 of Toner) Production Example 1 of Toner
, Except that the polyethylene wax was changed to 5 parts of polypropylene (maximum endothermic peak in DSC: 152 ° C., solubility test ×) in the same manner as in Production Example 1 of the toner. To obtain toner particles
Mixing hydrophobic silica fine powder and conductive fine powder to form toner J
Was prepared. Tables 2 and 3 show the formulation and physical properties of Toner J. The electron microscopic observation of the toner J revealed that no magnetic powder was exposed.

(Production Example 11 of Toner) Production Example 1 of Toner
In 100 parts of the obtained toner particles, silica having a primary particle size of 8 nm was treated with hexamethyldisilazane on the surface, and 1.2 parts of hydrophobic silica fine powder having a treated BET value of 250 m ² / g was used. The conductive fine powder was mixed with a Henschel mixer (Mitsui Miike Kakoki Co., Ltd.) to prepare toner K. Tables 2 and 3 show the formulation and physical properties of Toner K. In addition, even when the toner K was observed with an electron microscope, the magnetic powder was not exposed.

(Production Example 12 of Toner) Production Example 1 of Toner
In 100 parts of the obtained toner particles, a titanium oxide having a primary particle size of 82 nm was treated with hexamethyldisilazane on its surface, then treated with silicone oil, and the hydrophobic oxidation having a BET value of 130 m ² / g after the treatment was performed. Toner L was prepared by mixing 1.2 parts of titanium fine powder and conductive fine powder with a Henschel mixer (Mitsui Miike Kakoki Co., Ltd.). Tables 2 and 3 show the formulation and physical properties of Toner L. In addition, even when the toner L was observed with an electron microscope, the magnetic powder was not exposed. (Production Example 13 of Toner) In Production Example 1 of toner, 1.2 parts of untreated silica fine powder having a primary particle diameter of 8 nm and conductive fine powder were mixed with 100 parts of the obtained toner particles by a Henschel mixer (Mitsui Miike Chemical Co., Ltd.). Mixing with Toner M
Was prepared. Tables 2 and 3 show the formulation and physical properties of the toner M. The electron microscopic observation of the toner M did not reveal the magnetic powder.

(Toner Production Examples 14 to 17) In the toner production example 1, the conductive fine powder 3 was replaced with the conductive fine powder 1,
The toners N, O, P,
Q was prepared. Tables 2 and 3 show the formulations and physical properties of the toners N, O, P, and Q.

(Comparative Production Example 1 of Toner) Styrene / n-butyl acrylate copolymer (mass ratio 80/20) 100 parts Unsaturated polyester resin used in Production Example 1 of toner 2 parts Saturated polyester resin 3 parts Negative charge Properties control agent (monoazo dye-based Fe compound) 1 part Surface-treated magnetic powder 1 90 parts Ester wax used in Toner Production Example 1 5 parts Polyethylene wax used in Toner Production Example 1 5 parts The above materials were used in a blender. The mixture was melted and kneaded with a biaxial extruder heated to 110 ° C., and the cooled kneaded material was coarsely pulverized by a hammer mill, and the coarsely pulverized material was finely pulverized by a jet mill and classified by wind power to obtain a weight average particle diameter of 8%. 0.0 μm of non-spherical toner particles were obtained. Next, the obtained non-spherical toner particles 1
A mixture obtained by adding 1.2 parts of the hydrophobic silica used in Toner Production Example 1 and conductive fine powder to 00 parts was mixed with a Henschel mixer to prepare a toner R. Tables 2 and 3 show the formulation and physical properties of Toner R. In the electron microscopic observation of the toner R, the magnetic powder was partially exposed, which suggested that the magnetic powder was not completely encapsulated.

(Comparative Toner Production Example 2) In the formulation of Toner Production Example 1, the formulation of ester wax and polyethylene wax was changed to polyethylene wax (maximum endothermic peak in DSC of 128 ° C., solubility test ×). Other than the above, toner particles having a weight average particle size of 7.8 μm were obtained in the same manner as in Production Example 1 of the toner, and the hydrophobic silica fine powder used in the Production Example 1 of the toner and the conductive fine powder were mixed. Was prepared. Tables 2 and 3 show the formulation and physical properties of the toner S. In addition, even when the toner of the toner S was observed with an electron microscope, the magnetic powder was not exposed.

(Comparative Production Example 3 of Toner) In the same manner as in Production Example 1 of the toner, except that the magnetic powder was changed to the magnetic powder 1 not hydrophobized in the formulation of the Production Example 1 of the toner. Toner particles having an average particle diameter of 6.9 μm were obtained, and the hydrophobic silica fine powder and the conductive fine powder used in Production Example 1 of the toner were mixed to prepare a toner T. Tables 2 and 3 show the formulation and physical properties of the toner T. In the electron microscopic observation of the toner T, the magnetic powder was partially exposed,
It was suggested that the magnetic powder was not completely encapsulated.

(Comparative Production Example 4 of Toner) A toner U was prepared in the same manner as in Production Example 1 of the toner except that the conductive fine powder 3 was changed to resin particles having a resistance of 10 ¹² Ω · cm. Tables 2 and 3 show the formulation and physical properties of Toner U.

The magnetic field of the obtained magnetic toner was 79.6 k.
The magnetization intensity at A / m is 26-30 Am
² / kg. Further, the content of the iron element (B) with respect to the content of the carbon element (A) existing on the surface of the toners A to Q, the toner S, and the toner U measured by ESCA (X-ray photoelectron spectroscopy). The ratio (B / A) was 0.001 or less, but the toner R was 0.0032,
Toner T was 0.0057.

[0431]

[Table 2]

[0432]

[Table 3]

(Photoreceptor Production Example 1) A photoreceptor having a diameter of 3
A 0 mm Al cylinder was used as a substrate. Then, layers having the structure shown in FIG. 3 were sequentially laminated by dip coating to prepare a photoreceptor. (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 ( 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 was 95 degrees. In addition, pure water was used for the measurement of the contact angle, and a contact angle meter CA-X manufactured by Kyowa Interface Science Co., Ltd. was used for the apparatus.

(Embodiment 1) As an image forming apparatus, LBP
-1760 was modified and used generally as shown in FIG. The organic photoconductor (OPC) drum of Photoconductor Production Example 1 was used as the electrostatic image carrier. A rubber roller charger coated with a nylon resin in which conductive carbon is dispersed as a primary charging member is brought into contact with the photoreceptor (contact pressure 60 g /
cm), DC voltage -700 Vdc and AC voltage 2.0 kV
A bias on which pp 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 Vd was -680 V and the bright portion potential VL was -130 V.

The gap between the photosensitive drum and the developing sleeve is 29
It was set to 0 μm. This developing sleeve has a structure in which a resin layer having a layer thickness of about 7 μm and a JIS center line average roughness (Ra) of 1.0 μm having the following structure as a toner carrier is formed on a 16 mm diameter aluminum cylinder having a blasted surface. The developing sleeve has a developing magnetic pole of 85 mT (8
50 gauss), a thickness of 1.0 mm as a toner regulating member,
29. A silicone rubber blade having a free length of 1.0 mm was used.
The contact was performed at a linear pressure of 4 N / m (30 g / cm). Phenol resin 100 parts Graphite (particle size: about 7 μm) 90 parts Carbon black 10 parts

Next, as a developing bias, a DC bias component Vdc = −400 V, a superposed AC bias component Vpp−p = 1600 V, and f = 2000 Hz were used.
The peripheral speed of the developing sleeve is the peripheral speed of the photoconductor (94 mm / s).
ec) in the forward direction at a speed of 105% (103 m
m / sec).

Also, 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 Ωcm, 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).
Rotate at a constant speed to c). The transfer bias was DC 1.5 kV.

As a fixing method, an LBP-1760 fixing device which does not have an oil application function and uses a heater to heat and pressurize through a film for fixing is 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 18
The nip width was set to 7 mm at 0 ° C.

First, using toner A as toner,
An image extraction test was performed in an environment of 2.5 ° C. and 80% RH. 90 g / m ² paper was used as the transfer material. As a result, high transferability was exhibited at the initial stage, and a good image without fog on non-images was obtained without any missing characters or lines during transfer.

Next, durability was evaluated using an image pattern consisting of only horizontal lines having a print area ratio of 4%. Image evaluation was performed as follows.

(Toner Fusion) Evaluation of toner fusion was made based on an image defect due to toner fusion on a halftone image in which an image defect is likely to appear, that is, a durable sheet in which black spots or white spots occurred. The larger the number of durable sheets before occurrence, the better the durability of the image forming method.

(Transfer Efficiency) Transfer efficiency is determined by measuring the Macbeth density value of the toner remaining on the photoreceptor after the solid black image transfer by taping with a Mylar tape and peeling it off on paper, and C before transfer and fixing before transfer. When the Macbeth density of the Mylar tape pasted on the paper carrying the toner is D and the Macbeth density of the Mylar tape pasted on the unused paper is E, it was approximately calculated by the following equation.

(Equation 6) If the transfer efficiency is 90% or more, there is no problem in the image.

(Image Quality) The image quality judgment criteria are based on comprehensive evaluation of image uniformity and fine line reproducibility.

The uniformity of the image is determined based on the solid black image and the halftone image. A: A clear image with excellent fine line reproducibility and image uniformity. ：: A good image, although the reproducibility of fine lines and the uniformity of the image were slightly inferior. Δ: Practical image quality with no problem. X: An image that is poor in practical use because of poor reproducibility of fine lines and image uniformity.

(Fogging) The measurement of fog was carried out using a REFLECTMETER MODEL TC-6D manufactured by Tokyo Denshoku Co., Ltd.
Measured using S. A green filter was used as a filter, and fog was calculated by the following equation.

(Equation 7) Fog is a good image if it is 2.0% or less.

(Image Density) Image density was measured by Macbeth densitometer R
D918 (manufactured by Macbeth). The image density was evaluated based on the image density of the first sheet (the 20th sheet) and the image density of the first sheet which was left for two days after printing out 6000 sheets and then turned on again.

(Fixing property) The offset property is durability 1000
Stain generated on the back side of the image sample after the sheet was observed, and the degree of back stain of the obtained printout image was evaluated based on the following. A: not generated B: hardly generated C: slightly generated, but practically no problem D: considerably generated, practically problematic

As a fixing rubbing test, the toner weight per unit area was adjusted to 1.0 mg / cm ² on A4 plain paper (105 g / m ² ) for a copying machine, and a 10 mm × 10 mm solid for density measurement was measured. An image having a large number of images was output, and the obtained fixed image was rubbed five times with a silbon paper with a weight of 50 g / cm ² , and the image density reduction rate after rubbing was evaluated based on the following. A: less than 2%, B: 2% or more and less than 5% C: 5% or more and less than 10% D: 10% or more

Table 4 shows the obtained results.

[0450]

[Table 4]

(Examples 2 to 13) Image formation was performed in the same manner as in Example 1 except that toners B, C, D, E, F, G, H, I, J, K, L, and M were used as toners. The test was performed. As a result, a practically satisfactory result was obtained as shown in Table 4.

(Examples 14 to 17) An image forming test was performed by using the toners N, O, P, and Q as the toner and by the same image forming method as in Example 1. As a result, a practically satisfactory result was obtained as shown in Table 4.

(Comparative Example 1) An image forming test was performed in the same manner as in Example 1, except that toner R was used as the toner. As a result, an image having a slightly lower image density, lower transferability and lower dot reproducibility was obtained. Table 4 shows the results.

(Comparative Example 2) An image forming test was performed in the same manner as in Example 1 except that toner S was used as the toner. As a result, the stain on the back side of the image after 1000 sheets of durability was poor, and the number of toner-fused sheets was as large as 5500 sheets. Table 4 shows the results.

(Comparative Example 3) An image forming test was performed in the same manner as in Example 1 except that toner T was used as the toner. As a result, the image density was low from the beginning, and the stain on the back of the image after the endurance of 1,000 sheets was also deteriorated. Table 4 shows the results.

(Comparative Example 4) An image forming test was performed in the same manner as in Example 1 except that toner U was used as the toner. As a result, an image having high transferability at the initial stage, but having a low density was obtained. In addition, the number of generated toner fusion sheets was as large as 4500 sheets. Table 4 shows the results.

The magnetic toner of the present invention is also applicable to a cleanerless image forming method or a developing and cleaning image forming method. Hereinafter, the present invention will be described with reference to specific examples, but the present invention is not limited thereto. First, an example of manufacturing a photoreceptor as an image carrier used in an embodiment of the present invention will be described.

(Photoreceptor Production Example 2) The photoreceptor is a photoreceptor using an organic photoconductive material for negative charging (hereinafter referred to as an OPC photoreceptor), and has a base made of an aluminum cylinder having a diameter of 30 mm. Then, layers having the structure shown in FIG. 8 were successively laminated by dip coating to prepare a photoreceptor.

The first layer is a conductive particle-dispersed resin layer having a thickness of about 20 μm, which is provided to smooth defects of the aluminum cylinder and to prevent the occurrence of moire due to the reflection of laser exposure. (Mainly one in which tin oxide and titanium oxide powders are dispersed in a phenol resin).

The second layer is a positive charge injection preventing layer (undercoat layer), which serves to prevent positive charges injected from the aluminum support from canceling out negative charges charged on the surface of the photoreceptor. 10 ⁶ Ω by methylated nylon
A medium resistance layer having a thickness of about 1 μm, the resistance of which is adjusted to about cm.

The third layer is a charge generation layer, and is a layer having a thickness of about 0.3 μm in which a disazo pigment is dispersed in butyral resin, and generates a positive / negative charge pair upon receiving laser exposure.

The fourth layer is a charge transporting layer having a thickness of about 25 μm in which a hydrazone compound is dispersed in a polycarbonate resin.
And 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.

The fifth layer is a charge injecting layer, which comprises a photo-curable acrylic resin and conductive tin oxide ultrafine particles and a particle size of about 0.2.
It is a dispersion of 5 μm tetrafluoroethylene resin particles. Specifically, tin oxide particles having a particle diameter of about 0.03 μm, which has been doped with antimony and reduced in resistance, are added to the resin in an amount of 1%.
00% by mass, 20% by mass of ethylene tetrafluoride resin particles, and 1.2% by mass of a dispersant. The coating liquid thus prepared was applied to a thickness of about 2.5 μm by a spray coating method, and cured by light irradiation to form a charge injection layer.

The surface resistance of the obtained photoreceptor was 5 × 10 ¹²
Ω · cm, and the contact angle of the photoreceptor surface with water was 102 degrees.

(Photoconductor Production Example 3) Fifth Embodiment of Photoconductor Production Example 2
A photoreceptor was produced in the same manner as in Photoreceptor Production Example 1, except that the tetrafluoroethylene resin particles and the dispersant were not dispersed in the layer. As a result, the volume resistance value of the photoconductor surface layer becomes 2
× 10 ¹² Ω · cm, contact angle of the photoreceptor surface with water is 7
8 degrees.

(Photoconductor Production Example 4) The fifth example of Photoconductor Production Example 1
A photoreceptor was added, except that antimony-doped, low-resistance tin oxide particles having a particle size of about 0.03 μm dispersed in 300 parts by mass with respect to 100 parts by mass of a photocurable acrylic resin were added to the layer. A photoconductor was prepared in the same manner as in Production Example 1. In this case, the volume resistance value of the photoconductor surface layer was 2 × 10 ⁷ Ω · cm, and the contact angle of the photoconductor surface with water was 88 degrees.

(Example 5 of Photosensitive Member Production)
Photoconductor Production Example 1 except that a photoconductor having a four-layer structure having a charge transport layer as the outermost layer without a layer (charge injection layer) was provided.
A photoreceptor was produced in the same manner as described above. In this case, the volume resistivity of the photoconductor surface layer was 1 × 10 ¹⁵ Ω · cm, and the contact angle of the photoconductor surface with water was 73 degrees.

Next, an example of manufacturing the charging member used in the embodiment of the present invention will be described. (Production Example 1 of Charging Member) SU with a diameter of 6 mm and 264 mm
The S roller is used as a core, and a urethane resin, carbon black as a conductive particle, a sulfide agent, a foaming agent and the like are formed on the core to form a medium-resistance urethane foam layer in a roller shape, and further cut and polished to form a roller. The surface properties were adjusted, and a charging roller having a diameter of 12 mm or 234 mm was produced 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. When the surface of the charging roller was observed with a scanning electron microscope, the average cell diameter was about 100 μm, and the porosity was 60%.
%Met.

(Production Example 2 of Charging Member) Diameter 6 mm, 26
A 4 mm SUS roller was used as a core metal, and a tape in which conductive nylon fibers were piled on the core metal was spirally wound around a metal core metal to prepare a roll-shaped charging brush. The resistance of the fiber was adjusted by dispersing carbon black in nylon fiber, the fiber thickness was 6 denier (300 denier / 50 filament), the brush fiber length was 3 mm,
The brush density used was 100,000 brushes per square inch. The resistance value of the obtained charging brush roll is 1 ×
It was 10 ⁷ Ω · cm.

(Embodiment 18) In this embodiment, the developing and cleaning image forming apparatus shown in FIG. 5 was used. In this embodiment, the photoconductor of Photoconductor Production Example 2 is used as the image carrier,
As the charging member, the charging roller of Production Example 1 for the charging member was used.

In the present embodiment, one toner cartridge
20 g of toner A is filled and 2% coverage of 300 g
It was used until the amount of magnetic toner in the toner cartridge was reduced by zero intermittent printing. A4 copy paper of 75 g / m ² was used as the transfer material.
No printing was performed, but no decrease in developability was observed.

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

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

In addition, since the photosensitive member having the volume resistance of the outermost surface layer of the photosensitive member production example 2 of 5 × 10 ¹² Ω · cm of the photosensitive member production example 2 is used as the image bearing member, a sharp outline is maintained by maintaining an electrostatic latent image. Is obtained, and the direct injection charging which can obtain a sufficient charging property even after 3000 sheets of intermittent printing can be realized.
The photoconductor potential after direct injection charging after 3000 sheets of intermittent printing is -670 V with respect to the applied charging bias of -700 V.
The decrease in chargeability from the beginning was as small as 10 V, and no deterioration in image quality due to the decrease in chargeability was observed.

Further, in combination with the use of the photoconductor of Photoconductor Production Example 2 in which the contact angle of water on the surface of the image carrier with water was 102 degrees, the transfer efficiency was very high both at the initial stage and after 3000 sheets of intermittent printing. It was excellent. Considering that the amount of the residual toner on the photosensitive member after the transfer is small, the residual toner on the charging roller 2 after the intermittent printing of 3000 sheets is very small, and the fog of the non-image portion is small. Than that
It can be seen that the recoverability of the transfer residual toner in the development was good. Further, even after 3000 sheets of intermittent printing, scratches on the photoreceptor were slight, and image defects corresponding to the scratches on the image were suppressed to a practically acceptable level.

Hereinafter, a method for evaluating a printed image will be described. (1) Image Density After the initial and the intermittent printout of 3000 sheets were completed, the image was evaluated by the image density of the first sheet which was left for two days and turned on again. The image density is "Macbeth reflection densitometer"
(Manufactured by Macbeth Co., Ltd.), the relative density for the printout image of the white background portion where the document density was 0.00 was measured.

(2) Image fog The fog density (%) was calculated from the difference between the whiteness of the white background portion of the printout image and the whiteness of the transfer paper measured by a “Reflectometer” (manufactured by Tokyo Denshoku Co., Ltd.). Image fog was evaluated. A: very good (less than 1.5%) B: good (more than 1.5% to less than 2.5%) C: normal (more than 2.5% to less than 4.0%) D: bad (4%) that's all)

(3) Transferability The transferability was determined from the Macbeth density of a tape obtained by tapping the transfer residual toner on the photoreceptor at the time of forming a solid black image with a Mylar tape and affixing the stripped Mylar tape on paper. The evaluation was made by subtracting the Macbeth density from the paper only pasted on paper. A: very good (less than 0.05) B: good (more than 0.05 to less than 0.1) C: normal (more than 0.1 to less than 0.2) D: bad (more than 0.2)

(4) Chargeability After the initial stage and after the completion of the printout test, the surface potential of the photoreceptor after uniform charging was measured by arranging a sensor at the developing device position, and the chargeability was evaluated based on the difference. The larger the difference is, the larger the decrease in chargeability is.

(5) Intervening amount of conductive fine powder at the contact portion between image carrier and charging member The amount of conductive fine powder at the contacting portion between photoreceptor and charging member was measured by the method described above. . 10 ⁴ -5 × 10 ⁵ pieces / m
An intervening amount of m ² is preferred.

(6) Photoreceptor Scratches After the printout test was completed, the occurrence of scratches on the photoreceptor drum surface and the adhesion of toner to the scratches and the effect on the printout image were visually evaluated. A: very good (not generated) B: good (slight flaws are seen, but there is no effect on the image) C: normal (there is toner adhesion or flaws, but little effect on the image) D : Bad (many toner adhered along the scratch, resulting in a vertical streak-like image defect) The results are shown in Table 5. As can be seen from Table 5, good results were obtained in this example.

(Examples 19 to 21) In place of the photoreceptor of Photoreceptor Production Example 2 used in Example 18, Photoreceptor Production Examples 3 to
An image output test was performed in the same manner as in Example 18, except that the photoconductor obtained in Example 5 was used. Table 5 shows the results.

In Example 19 using Photoconductor Production Example 3,
As compared with Example 18, a good image was obtained although the transferability was slightly inferior.

In Example 20 using Photoconductor Production Example 4,
Compared with Example 18, the sharpness of the outline of the toner image was slightly inferior, but other than that, it showed almost good performance.

In Example 21 using Photoconductor Production Example 5,
Compared with Example 18, the charging efficiency was poor from the beginning, and the photosensitive member surface potential after charging was slightly inferior to the applied charging bias power supply of -700 V at -660 V from the beginning. Also, 300
After the end of the zero intermittent printout, the photoreceptor had a wider and deeper scratch than in Example 18.

Example 22 An image was formed in the same manner as in Example 18 except that the brush charging member obtained in Charging Member Manufacturing Example 2 was used instead of the charging member of Charging Member Manufacturing Example 1 used in Example 18. A take-out test was performed (FIG. 6). Table 5 shows the results. Compared with Example 18, the amount of the conductive fine powder present in the contact portion between the photosensitive member and the charging member was slightly smaller, and a good image was obtained although the charging uniformity was poor.

(Examples 23 to 25) Instead of the toner A used in Example 18, the toner B shown in Table 2 and Table 3 was used.
An image-drawing test was performed in the same manner as in Example 18 except that D and K were used. Table 5 shows the results.

(Examples 26 to 28) Operations were performed in the same manner as in Example 18 except that toners E, F, and H were used instead of toner A used in Example 18. Table 5 shows the results.

(Examples 29 to 32) The same operations as in Example 18 were carried out except that toners M, N, O and P were used instead of toner A used in Example 18. Table 5 shows the results.

(Comparative Example 5) Toner A used in Example 18
Was carried out in the same manner as in Example 18, except that the toners Q shown in Tables 2 and 3 were used instead of. Table 5 shows the results. Comparative Example 5 using Toner Q is Example 18
The image density was slightly low from the beginning, and the amount of fog and transfer residual toner was very large and unacceptable. In addition, the charging roller was contaminated with toner during the intermittent printing of 100 sheets, causing significant charging failure.

(Comparative Example 6) Toner A used in Example 18
Was carried out in the same manner as in Example 18, except that the toners R shown in Tables 2 and 3 were used instead of. Table 5 shows the results. Comparative Example 6 using the toner R is Example 18
Although the initial image density was slightly lower than that of the above, fog and transfer residual toner were in a range where there was no practical problem. But,
As the number of durable sheets increases, the image density further decreases, and
The charging roller is contaminated with toner by zero intermittent printing,
Significant charging failure occurred.

(Comparative Example 7) Toner A used in Example 18
Was performed in the same manner as in Example 18, except that the toners S shown in Tables 2 and 3 were used instead of. Table 5 shows the results. Comparative Example 7 using Toner S is Example 18
The image density was slightly low from the beginning, and the amount of fog and transfer residual toner was very large and unacceptable. In addition, the charging roller was contaminated with toner during the intermittent printing of 100 sheets, causing significant charging failure.

(Comparative Example 8) Toner A used in Example 18
Was carried out in the same manner as in Example 18 except that the toners T shown in Tables 2 and 3 were used instead of. Table 5 shows the results. Comparative Example 8 using toner T is the same as Example 18
From the beginning, the image density was clearly low compared to, and the image was unacceptable. Also, as the number of durable sheets increases,
At the same time as the image density further decreased, fog on the drum and transfer residue gradually increased, and the charging roller was contaminated with toner during intermittent printing of 1000 sheets, causing significant charging failure.

[0494]

[Table 5]

[0495]

According to the present invention, in the contact-charging type image forming method, the magnetic powder having the inorganic fine powder and the conductive fine powder on the surface is not substantially exposed to the surface and has an average circular shape. Degree of resolution is 0.960 or more, and high quality resolution is achieved by using a special magnetic toner that contains two types of wax that are soluble and insoluble in the monomer that is a component of the binder resin. An image having high fog, excellent fog, transferability and fixability can be obtained.

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

Further, using a simple member as the charging member, regardless of the contamination of the charging member by the transfer residual toner,
Ozone-less direct injection charging can be stably maintained at a low applied voltage for a long period of time, uniform charging properties can be provided, and there are no obstacles due to ozone products, poor charging, etc. An inexpensive image forming apparatus can be obtained.

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

Further, according to the present invention, the amount of waste toner can be greatly reduced by using the developing step of recovering the transfer residual toner in the preceding step, and the developing and developing method which is advantageous in reducing the size of the apparatus at low cost. A cleaning image forming method can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an example of an image forming apparatus that realizes an image forming method of the present invention.

FIG. 2 is a view showing a developing device shown in FIG. 1;

FIG. 3 is a schematic view showing an example of an image carrier used in the image forming method of the present invention.

FIG. 4 is a diagram illustrating an example of a transfer roller used in a transfer step in the image forming method of the present invention.

FIG. 5 is a schematic view showing an example of an image forming apparatus for realizing a developing and cleaning image forming method in the image forming method of the present invention.

FIG. 6 is a schematic view showing an example of an image forming apparatus having a brush charger for realizing a developing and cleaning image forming method used in an embodiment of the present invention.

FIG. 7 is a graph showing an example of charging efficiency of contact charging in electrophotography.

FIG. 8 is a layer configuration model diagram showing another example of the image carrier used in the image forming method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Aluminum base 12 Conductive layer 13 Positive charge injection prevention layer 14 Charge generation layer 15 Charge transport layer 16 Charge injection layer 16a Conductive particles (conductive filler) 21, 100 Photoconductor (image carrier) 22, 117 Charging roller (charging member) 22a, 34a Core bar 22 'Brush charging member (charging member) 23 Laser beam scanner 24 Developing device 24a, 102 Developing sleeve (toner carrier) 24b, 141 Stirring member 24c, 103 Elastic blade 25 Transfer roller 26 Fixing device 26a Heater 26b Fixing film 26c Pressure roller 27 Process cartridge 28 Cartridge holding member 34, 114 Transfer roller 34b Conductive elastic layer 35 Transfer bias power supply 104 Magnet roller 116 Cleaner 121 Laser generator 123 Laser light 24 register roller 125 conveyance belt 126 fuser 140 developing device P transfer material (recording medium)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 9/08 374 G03G 9/08 375 375 15/02 101 9/087 15/06 101 15/02 101 15 / 08 506A 15/06 101 9/08 101 15/08 506 384 507 15/08 507B (72) Inventor Keiji Kawamoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Magome Michihisa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Akira Hashimoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Tetsuhiko Chiba Inventor Tokyo 3-30-2 Shimomaruko, Ota-ku Canon Inc. F-term (reference) 2H003 BB11 CC05 CC06 DD03 2H005 AA02 AA06 AA08 AA15 AB06 CA12 CA13 CA14 CA26 CB07 C B13 DA07 DA09 EA01 EA02 EA03 EA05 EA07 2H068 AA05 AA06 AA08 BB03 BB31 BB33 CA37 FC01 FC08 FC11 FC15 2H073 BA03 BA13 BA43 CA02 2H077 AA37 AC16 AD06 AD36 BA07 EA13 EA16 GA03

Claims (41)

[Claims] A charging step of charging the image carrier by applying a voltage to a charging member that forms a nip portion with the image carrier and contacts the charging member with the image information as an electrostatic latent image on a charged surface of the image carrier. And a developing step of developing the electrostatic latent image with a magnetic toner carried on a toner carrier to form a toner image, and a transferring step of transferring the toner image to a recording medium. An image forming method, wherein the magnetic toner has at least a binder resin, a wax, and toner particles including a magnetic powder, an inorganic fine powder, and a conductive fine powder having an average particle size smaller than the toner particles. Having a mean circularity of 0.960 or more, wherein the magnetic powder is substantially not exposed on the surface of the toner particles, and the wax is at least a monomer constituting a binder resin. Soluble in water Image forming method, which comprises at least two types of boxes and the insoluble wax. 2. The image forming method according to claim 1, wherein the circularity of the magnetic toner is 0.970 or more. 3. A cross-sectional observation of a magnetic toner using a transmission electron microscope, wherein a projected area circle diameter of the magnetic toner is C, and a minimum value of a minimum distance between the magnetic powder and the surface of the toner particles is C. 2. The image forming method according to claim 1, wherein when D is satisfied, the number of toner particles satisfying the relationship of D / C ≦ 0.02 is 50% or more. 4. The image forming method according to claim 1, wherein the magnetic toner contains the wax in a total amount of 0.5 to 50% by mass based on the binder resin. 5. When the content of the soluble wax component is E parts by mass and the amount of the insoluble wax component is F parts by mass relative to 100 parts by mass of the binder resin, the wax is contained in the toner in an amount of 0.1 part by mass.
2. The image forming method according to claim 1, wherein the content is in the range of 5 ≦ E / F ≦ 100. 6. The method according to claim 1, wherein the soluble wax is a wax selected from the group consisting of ester wax, paraffin wax, microcrystalline wax, oxides of these waxes and derivative waxes. 3. The image forming method according to 1., 7. The method according to claim 1, wherein the insoluble wax is a wax selected from the group consisting of polyolefin wax, Fischer-Tropsch wax, montan wax, oxides of these waxes and derivative waxes. 2. The image forming method according to 1. 8. The image forming method according to claim 4, wherein the wax has at least one endothermic peak in the range of 45 ° C. to 150 ° C. by differential thermal analysis. 9. The magnetic toner has a mode circularity of 0.9.
The image forming method according to claim 1, wherein the number is 9 or more. 10. The image forming method according to claim 1, wherein a part or the whole of the toner particles in the magnetic toner is obtained by a polymerization method. 11. The magnetic toner has a magnetic field of 79.6 kA.
^2. The image forming method according to claim 1, wherein the intensity of magnetization at 10 g / m is 10 to 50 Am ² / kg. 12. The inorganic fine powder has an average primary particle size of 4 to
2. The image forming method according to claim 1, wherein the thickness is 80 nm. 13. The method according to claim 1, wherein the inorganic fine powder has an average primary particle size of 4 to 4.
13. The image forming method according to claim 12, comprising at least one kind of inorganic fine powder selected from 80 nm silica, titanium oxide, alumina, and a double oxide thereof. 14. The image forming method according to claim 1, wherein the inorganic fine powder is subjected to a hydrophobic treatment. 15. The image forming method according to claim 14, wherein the inorganic fine powder has been subjected to a hydrophobic treatment with at least silicone oil. 16. The image forming method according to claim 15, wherein the inorganic fine powder is treated with at least a silane compound and silicone oil. 17. The conductive fine powder has a resistance of 10 ⁹ Ω.
2. The image forming method according to claim 1, wherein the nonmagnetic conductive fine powder has a content of 0.2 to 10% by mass based on the whole magnetic toner. 3. 18. The conductive fine powder has a resistance of 10 ⁶ Ω.
18. The image forming method according to claim 17, wherein the non-magnetic conductive fine powder has a size of not more than cm. 19. The image forming apparatus according to claim 19, wherein the charging step is a step of charging the image carrier in a state where at least 10 ³ / mm ² or more conductive fine powders are interposed in a nip between the charging member and the image carrier. The image forming method according to claim 1, wherein: 20. The charging step, wherein the surface of the charging member forming the nip portion and the surface of the image carrier move with a relative speed difference to charge the image carrier. The image forming method according to claim 19, wherein: 21. The method according to claim 20, wherein the charging step is a step of charging the image carrier while the surface of the charging member and the surface of the image carrier move in directions opposite to each other.
2. The image forming method according to 1., 22. The charging step in which the Asker C hardness is 5
22. The image forming method according to claim 19, wherein the image carrier is charged by applying a voltage to a roller member having a temperature of 0 degrees or less. 23. The charging step, wherein the resistance is 10 ³ Ω · c.
23. The image forming method according to claim 22, further comprising a step of charging the image carrier by applying a voltage to a roller member having a length of m to 10 < ⁸ > [Omega] .cm. 24. The charging step, wherein the roller member has, at least on its surface, a depression having an average cell diameter of 5 to 300 μm in terms of sphere, and the porosity of the roller member surface having the depression as a void is The image forming method according to claim 23, wherein the amount is 15 to 90%. 25. The image forming apparatus according to claim 19, wherein the charging step is a step of charging the image carrier by applying a voltage to a conductive brush member. Image forming method. 26. The charging step, wherein a DC voltage or a discharge starting voltage in DC application is Vth, 2 ×
26. The image carrier according to claim 19, wherein the image carrier is charged by applying a voltage obtained by superimposing an AC voltage having a peak-to-peak voltage less than Vth (V) on a DC voltage to the charging member. An image forming method according to claim 1. 27. The charging step, wherein when a DC voltage or a discharge starting voltage in DC application is Vth, Vt
applying a voltage obtained by superimposing an AC voltage having a peak-to-peak voltage of less than h (V) on a DC voltage to the charging member, thereby charging the image carrier substantially without a discharge phenomenon. The image forming method according to any one of claims 19 to 26. 28. The image forming method according to claim 1, wherein the outermost layer of the image carrier has a volume resistance of 1 × 10 ⁹ Ω · cm or more and 1 × 10 ¹⁴ Ω · cm or less. 29. The image forming method according to claim 28, wherein the outermost surface layer of the image carrier is a resin layer in which conductive fine particles containing at least a metal oxide are dispersed. 30. The image forming method according to claim 28, wherein a contact angle of the surface of the image carrier with water is 85 degrees or more. 31. The image forming apparatus according to claim 30, wherein the outermost surface layer of the image carrier is a layer in which lubricant fine particles selected from at least a fluorine-based resin, a silicone-based resin, and a polyolefin-based resin are dispersed. Image forming method. 32. The image forming method according to claim 28, wherein the image carrier is a photoconductor using a photoconductive substance. 33. The image forming method according to claim 1, wherein the latent image forming step is a step of writing image information as an electrostatic latent image on a charged surface of the image carrier by image exposure. 34. The image forming apparatus according to claim 1, wherein said developing step also serves as a cleaning step of collecting magnetic toner remaining on the image carrier after transferring the toner image onto a recording medium. Method. 35. The developing step comprises:
35. The image forming method according to claim 1, comprising forming a toner layer of about 30 g / m < ² >, transferring the toner from the toner layer to an image carrier, and developing an electrostatic latent image. 36. The image forming method according to claim 34, wherein in the developing step, a gap between the image carrier and the toner carrier is 100 to 1000 μm. 37. 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 the toner is transferred from the toner layer to the image carrier to form a static image. The image forming method according to any one of claims 34 to 36, wherein the method is a step of developing an electrostatic latent image. 38. The developing step includes a step of applying at least an alternating voltage as a developing bias between the toner carrier carrying the toner and the image carrier to develop the electrostatic latent image on the image carrier with the toner. The alternating electric field has an electric field intensity between peaks of 3 × 10 ⁶ to 1 × 10 ⁷ V / m and a frequency of 100
The image forming method according to any one of claims 34 to 37, wherein the frequency is from 5000 Hz to 5000 Hz. 39. The transfer step according to claim 1, wherein the transfer member is a step of bringing the recording medium into contact with the image carrier at the time of transfer, and transferring the toner image on the image carrier to the recording medium. 3. The image forming method according to 1., 40. The conductive fine powder contained in the magnetic toner adheres to the image carrier in the developing step, remains on the image carrier after the transfer step, and is transported at least in the charging step. 2. The image forming method according to claim 1, wherein the image forming apparatus is provided at at least one of a nip portion between the charging member and the image carrier and a vicinity thereof. 41. A magnetic toner used in the image forming method according to claim 1, wherein the magnetic toner contains at least a binder resin, a wax, and a magnetic powder. And an inorganic fine powder, and a conductive fine powder having an average particle diameter smaller than the toner particles, the average circularity is 0.960 or more, and the magnetic powder is substantially exposed to the toner particle surface. A magnetic toner, wherein the wax contains at least two kinds of waxes, which are soluble in and insoluble in a monomer that is a component of the binder resin.